Throughout the guide I will often refer to growth rates as great, good, medium or poor. Tracking down exact growth rates is difficult as many skills do not follow a simple growth pattern. It is also impossible to de-level a skill so I cannot compare before and after skill levels without starting a completely new game/account and then unlocking all of the heroes again.

I realize the lack of hard data is not ideal.

Furthermore heroes gain something called "favor" which increases their stats. With no way to prevent gaining favor it's difficult to ascetain base stats and reverse calculate.

In other words, short of the developers themselves giving us the numbers, it is difficult to get exact growth rates for most skills.

Aiden is one of the heroes you begin with; he is a paladin and as such has high health but low damage. He is your standard party tank and does a resonable job of it, being more of an all-rounder rather than a specialist, able to heal others, reduce party damage, heal himself and with a passive that reduces damage taken.

Aiden works well with Emma or any other "silence" user.

Rejuvenating Strike
Recovering half the damage inflicted in order to heal yourself is powerful in any game and this is no different. Works well with Aiden's ability to sacrifice health to heal party members HOWEVER its scaling is poor and even if it wasn't, as a paladin, Aiden is NOT rolling in MP to really abuse this skill. You will see me mention this numerous times and it is really Aiden's greatest weakness.

Guardian
For the current and following turn, Aiden takes all damage directed at the party and that damage is reduced by 20%. The scaling on this skill is great, not just in itself but because it also works alongside Aidens passive, to offer a 2nd, further damage reduction. Guardian can carry you through tough battles...If only Aiden had the MP! A solid skill however, comes in useful for the last story mission.

Sacrifice
Aiden gives up a portion of his health in order to heal a team mate for the same amount. Can kill yourself with it. If you want Aiden to run as the party healer (a triple paladin party for example) then this is needed for it, however outside of that its a pretty lackluster skill. You are probably sick of reading it but Aidens MP is a constant, consistant problem. Every time you level up his skills the MP cost goes up as well so the number of times you can use these skills becomes smaller, not larger.

Divine Shield (Passive)
Reduces melee attacks but NOT skill damage. Provides a seperate, further reduction to damage taken from Guardian. Scales poorly but starts at 20%.

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Aiden in general is a good Paladin and if you carry 4 mana pots at all times he is more than capable of being a great tank + healer rolled into one. You do need to dedicate to mana on him or else he becomes a dead weight! Paladins don't hit hard in general. Also the Guardian skill reduces the damage you take when using Sacrifice too.

Emma

Final Word
Silences all foes below level 1 with a 50% chance on foes above that level.
Don't be fooled by that level 1, it scales to match Emma's level if you level it up which you should. Monsters LOVE to go to town with poison, freeze, sleep, basically nasty stuff. Furthermore since they are classed as skills and not attacks, they often bypass things that only work against attacks. You can live without silence but it becomes really painful to do so in mid-tier poison happy dungeons.

Static Storm
A rubbish AOE skill with poor scaling, however it is all you get to start out with so may as well make the most of it. Its not terrible but there is better on offer on other mages and Emma isn't very good overall outside of that silence.

Arcane Bolt
Scales rather brilliantly actually, just one problem, it only hits 1 foe at a time. Mainly for blowing up bosses and nothing else, which is not very good since wiping out groups of mobs is 90% of the game!

Spell Consume(passive)
Get hit by a skill and gain MP.
This is why you will bench Emma! You don't ever want to get hit by skills because none of them are nice. Futhermore, silence prevents enemy mobs using skills, so this only triggers when you fail to silence everyone and that is probably because you are out of MP. Other mages blow this passive out of the water and mages are super squishy so she isn't best suited to getting hit in the face! Also because the skill couldn't get bad enough, it has a upper cap on how much MP you can absorb in any one fight! Every other mage has a better passive than this!

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Emma suffers from trying to find a home. Her silence is great but you start the game with her so its too early to put it to use and by the time you would use it, you have already benched her! Her nukes are up-staged by rouges and mages alike and her passive is rubbish. Easily the worst mage in the game! Silence is her ONLY claim to fame and thankfully for her, it works great with Aiden. Her single target damage is no joke either.

Mila is your first healer and she will last you a very long time! Maybe even all the way to the end of the game, but that requires dedication to make her work that long.

Breath of Life
Heal an ally this turn and the following 2 turns or steps. This skill ends if you end combat before it resolves. Highly mana efficient in its scaling, very effective due to being a heal over time and overall a great skill. Highly recommended.

Divine Fury
Adds the blind status effect to one foe and deals damage. The blind reduces damage from the target by 30% but enemies begin to hit so hard that it doesn't matter later on. It helps a certain rogue do more damage however and also gives her something to do in boss fights.

Redemption
heals an ally and gives them +40% damage (non-stacking) until the end of combat.
Only the damage lasts until end of combat, you have to keep healing the ally if you want them to stay alive. Alongside Divine Fury, Mila has a lot to do during boss battles, MP allowing.

Healing Wrath(passive)
Heal an ally for a percentage of the damage you deal.
This skill is single handedly the reason why Mila is so great, boosting her attack power also increases the party staying power and the scaling is medium which is pretty great too! Redemption will make this passive heal for more since it boosts her damage and she makes boss fights a breeze!
Just one problem, being designated as a healer, her damage output isn't massive anyway so trying to boost it to be better is difficult.

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I really like Mila and resisted replacing her for the longest time. Works exceptionaly well in a Aiden, Emma, Mila team and it is very important you keep her with Emma if you can because she has no status effect removal, which becomes a huge problem as you advance in the game.

Sarith is a Rogue and one of the first that you get and a great one to start with too.

Frozen Venom
Freezes (slow) and poisons a foe. By itself a mediocre skill but combined with opportune Blow, its a real powerhouse of a boss killer! One shotting some early dungeon bosses and carrying you easily into midgame.

Opportune Blow
For every status effect this attack does bonus damage.
The skill already has nice damage, scales really well, and then the bonus damage is just insane. Sarith works excellently alongside any Hero that inflicts status effects thanks to this move alone.

Acid Rain
deal damage to all foes, deal the same damage over the next 2 turns.
This skill scales nicely and does a lot of damage HOWEVER it gets shown up by later attacks that just outright wipe enemy squads in one or two hits and at that point you really need to bench Sarith.
The fact the damage is delayed on this skill is its biggest failing as it is the strongest AOE in the game in terms of raw numbers but having to wait for things to drop dead, makes this skill not so great.

Poisoned Blade
Your melee attacks deal bonus poisoned damage.
The damage comes on the next turn and scales very badly, overall, not worth investing in to be quite honest.

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Sarith can be your boss killer or your first realy powerful AOE user. He can even be both, MP permitting but he has 1 very serious flaw! poison is damage over time. Later in the game you want things dead on turn 1 (infact that is always the ideal scenario truth be told) so as he takes longer and longer to get his kills, he becomes more of a liability and despite having some of the highest damage in the game, the fact it isn't front loaded relegate him to a life in reserve.
Fantastic when he joins, when his damage begins to tamper off, its time to bench him i'm afraid.

Blinding Roar
Blinds all foes and deals damage.
Blind, despite what you might think, reduces damage by 30% rather than making enemies miss more. Still, its a nice reduction and the fact it hits everyone is even better. You have two main ways to use this skill, leave it at level 1 (recommended) and use it as AoE blind, or scale it up for more damage. A common theme with Virgil is that he is amazing with his skills at level 1 so never, ever level any of his skills up! This skill does very poor damage and scales horribly! In addition to not scaling well, it also increases in MP cost. Leave this one well alone at level 1, it works beautifully when it only costs 15MP

Taunt
On the turn taunt is used, or the opponents next turn, whichever comes first, that foe will attack Virgil and the damage will be reduced by 20%
This skill scales by 0.25 per level but again, its MP cost also scales with it. Between this and blinding roar, Virgil is a more offensive paladin, throwing out damage, utility and being all around useful. It is not documented anywhere but this skill also prevents the enemy from using skills on the turn it is used, they must melee attack Virgil making it act as a 1 turn silence.

Battle Cry
Increases the attack of all party members, stacks upto three times.
Repeat after me, I will never, ever, level this skill up! The damage is huge on this one and I make it a habit to use it 3 times against bosses and even once against higher HP enemies! I highly recommend this skill because its really great! It does have medium scaling but the MP scaling is also medium and with Virgil's tiny MP pool, it hurts to level too much.

Flame Shield(passive)
Enemies who hit Virgil take burning damage for the next two turns.
This skill right here is Virgils bread and butter! It scales fantastically and the damage dealt is no joke! Furthermore because its his passive, any investment in this skill pays off!

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Virgil is your offensive paladin. He does serious damage, causing 2 status effects, is a fantastic boss killer thanks to battle cry and is just generally a cool guy who doesn't afraid of anything!
I said it before but here I have to really stress it, Virgil has one of the lowest MP pools in the game, period! His skills cost more MP the more they level up and are already fantastic at level 1 anyway so don't level them up! Flame shield is the exception since it has no MP cost, being his passive and also does fantastic damage. Taunt will cause foes to hit him with a melee attack rather than a skill so its a psudo-silence that works on chest-bosses (chest-bosses are immune to most status effects) and really you will only bench Virgil because you get someone better or are really getting milage from Aiden.
I personally used Virgil for the longest time but sadly front loading damage is more efficient in the long run and so he now resides on the benches, awaiting his return to glory.

Ice Storm
Does medium damage and freezes all foes.
Syren is your utility mage, this is the biggest punch she will pack and while it is decent, you shouldn't use Syren as your main damage dealer. Scales decently.

Cleanse
Remove all status effects from a single party member.
Decent, you get better later on but if you are running with no healers then this is a very useful skill to have. Not really sure why you would ever level this skill up really, it works fine at level 1 anyway.

Maritime
Enemies affected must skip a turn.
Effects enemies upto lv2 and scales the more you level it, actually scales ahead, so at lv2 it will affect enemies upto lv3. It does have a chance to fail and frankly its quite a contrarian skill. You can either make the enemy skip a turn or pick someone else and just outright kill them.
Not really sure what to make of this one.

Echo(passive)
Returns a percentage of skill damage back at enemies.
Most skill attacks inflict status and very few except poison and burn, pack a big punch. You also don't want to be afflicted by them since they hurt a lot so as you can imagine, echo is pretty rubbish.

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Overall Syren is a solution looking for a problem. She offers a lot of utility in a game that doesn't care. Nuke every enemy and move on, turns wasted trying to debuff enemies is just a pointless waste of time! I never gave Syren much screen time because there was nothing for her to do. Your milage may vary.

Blinding Strike
Blinds and strikes an enemy.
This skill does big damage, the fact that it blinds is a nice bonus but isn't really relevent.

Assassin's Mark
Target foe takes 40% more damage.
Scales poorly but that isn't important, whats important is the damage boost. You can probably tell but Jera is your boss killer and nothing else.

Eviscerate
Inflicts massive damage on an enemy.
Scales massively, serves no other purpose than to hit hard.

Fixate(passive)
Jera has a 25% chance to attack the same target again.
This skill scales by 0.25 per point which is a huge shame because you will want to see this trigger often and it just never triggers when you really really want or need it too, polishing off weak foes instead or something equally as disappointing.

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Jera is your boss killer and nothing else. I am fine with this and she will serve you very well if you can find room to fit her in. Her main issue is that she doesn't really combo well with anyone nor does she bring any utility to the party, offering nothing more than high damage. She is hit or miss, you will either love her or bench her but her lack of flexibility is her downfall.

Shield Bash
does low damage and has a 50% chance to put foe to sleep
The damage on this is low, really low and it doesn't get any better with scaling so keep at level 1!
The chance to inflict sleep also doesn't seem to increase, further cementing the need to leave this skill well alone! However for what it's designed for, it does it very well and isn't a terrible skill at all.

Crushing Blaze
Hits all foes twice for damage.
the skill description is misleading this skill inflicts burning status on all foes, not 2 melee attacks. With that in mind it really tampers off, see poison stacks but burning does not so this conflicts with other burn inflicting heroes. Furthermore, the damage scales poorly and the MP cost shoots up. A very poor skill overall, one of the worst in the game at present.

Bulwark
Increases HP by X for all party members, does not stack.
Urm, not really sure what the point of this one is. The extra health is given to the party in full, so you don't need to heal on top IE: 1000hp, use bulwark, you now have 1500hp
I don't know why this skill exists, at the end of combat the extra HP is gone, as expected but I don't know why you would ever use this skill except the later dungeons when enemies hit like a mac truck and this skill has medium scaling and medium MP cost so even then, evern there, its of limited usefulness anyway!

Reflection(passive)
Reflects physical damage but not skills.
Percentage based reflection and only does melee attacks not skills. scales poorly.

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Thalion is one of those heroes who looks cool and sounds cool at first blush but is just garbage. It pains me to say it but most of the latter heroes can fill a role or do something useful, Thalion just gets in the way. He inflicts poor damage, as a paladin he lacks the MP to use skills often, the skills he does have are not very good anyway, he just fails at every turn.
Shield bash is his only saving grace and frankly you can do just fine without it, moreso with it failing to sleep 50% of the time!

Heart Seeker
Deals damage and increases Grey's critical chance by 50%
Like Jera before him, Grey is a dedicated boss killer, he is also a team player and can assist the team in other ways. If you were using Jera till now then its time to replace her. Heartseeker has great scaling too.

Shared Deception
The party gains 10% chance to dodge
has poor scaling but due to its defensive nature and the fact that it stacks upto 3 times anyway means you are going to benefit from either leaving it at lv1 or leveling it up.

Shadow Walk
Become untargetable (Grey only), your next attack gains +200% damage
Now it becomes clear why you will bench Jera for Grey. He does more damage than her and is more durable to boot. Level this if you want too, regardless of if you do or do not, its very useful!

Evade(passive)
Grey has a 10% chance to dodge attacks.
Low scaling as you would expect and as far as passives go its middle of the road. I mean there is worse! Emma has much worse!

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If you have been using a thief for this long then Grey is your new thief. Also works with Alaric very well!