Decided to do a fresh campaign playthrough with this mod installed - the below observations and commentary are made without malice and are dependent upon a particular style of play. Regarding the latter, I decided to drag out all campaign missions as much as possible to see as many endgame adventurers as possible.

Overall:
Many melee soldiers with the "Net" ability should have this ability's place exchanged with their primary attack option - the game defaults to "Net" at the beginning of every turn. Vaguely aggravating since every other unit has 1-move, 2-primary attack, 3-defense keybound.
Additionally, super classes such as Primus or Lithandra are limited to a single instance alive at any given time. Not sure if this is intended BUT IF IT IS, it should be kept this way. And if this is indeed the case, bravo on that particular foresight
Lastly, all tier 4 melee units should receive the War Cry ability (or something similar), assuming they do not have any other means of temporarily boosting damage.

Regarding High Elves:
Elite Band of Mercs needs a small health OR defense buff - personally I would suggest a 10 defense buff. Also, increase their damage by 2 to 3 and add the Martial Arts perk. In the current state it's just a mediocre Master of War, especially given the value of flanking attacks. And change the name. Might I suggest "Elite Vanguard"?
Lithandra should have her AoE heal increased from 15 to 20. Her AoE defensive buff (forget the name) should be increased to lasting for two turns, up from "until end of turn." In the current state, the defensive buff is hardly ever used. Offensive buff is fine.
Master of War fire/thunder infusions should have their cooldown increased to 3 turns, up from 2. Stance dancing should be somewhat penalized, especially since you can easily dash out of harm's way.
Priors damage should be increased by 1 to 2. They are an end-tree unit after all.

Regarding Humans:
To begin with, their progression tree is massively convoluted and, quite frankly, unnecessarily so. The units, at least at endgame, are well thought out but the path to endgame is extremely arbitrary. Might I suggest that each of the 3 starting adventurers (calculating/courageous/cunning) have their own distinct paths of progression until the third tier. For example, Cunning would evolve into, say, Profiteer, who could evolve into Ranger or *insert dagger class name* who would then evolve into two distinct engame classes or Primus.
In its current state, evolution for Humans is a dice roll with far too many odds. Case in point, I dragged on a mission for 300 turns and STILL hadn't seen every possible class.

Regarding Orcs:
Rename High Shamans. The game already has shaman classes, adding another is confusing as all hell. Might I suggest "Astralbound"?
Towering Death needs a nerf. Not sure if it's intended but the unit heals to full health at the start of your turn, every time. In its current state, Towering Death is ridiculously overpowered, especially if combined with hero traits and Heart of Iron. I suggest removing the "full health at beginning of turn" perk (forgot the name) and instead amping up Regeneration. Instead of 6 health, make it 20 to 25 and up the unit's defense by 5. Towering Death should still be killable under sustained fire.
Bruisers/Ravagers should NOT evolve back into Bruiser/Ravagers. With the amount of time it takes to evolve a tier 3, this evolving back into itself business is mildly infuriating.
Rename "Corrupted Elites." Boring. It's a tier 4 unit. Might I suggest "Onslaught"? Also, it needs a perk to make it stand out - I would suggest Martial Arts be added.

Regarding Goblins:
All tier 4 units need to be changed somewhat from tier 3 units. In their current states they're virtually identical, barring more health/dam/def. Might I suggest adding some perks to tell them apart, especially since you're going for a corrupted vs pure dynamic?
Corrupted Shadow Iron should be renamed. Might I suggest "Cursed?"
Blessed Shadow Iron should be renamed. Might I suggest "Favoured" or "Chosen"?
Corrupted Elite Alchemists should be renamed. Might I suggest "Consequentialist" or the name given to its counterpart, "Shademist"?
Corrupted Shadow Alchemists should be renamed to simply "Shadow Alchemists."
Blessed Alchemical Elites should be renamed. Might I suggest "Alchemical Wonder"?
Blessed Shademist should be renamed. Might I suggest "Ethicist"?
Cure Disease and Dispel abilities should be given to all alchemists.
Black Bolts ability should be given to all "dark alchemy" units.
Magic Bolts ability should be given to all "light alchemy" units.

I'll add more as I progress through the campaign. Props on the great mod though, I really love the variety it adds, human progression malarchy notwithstanding.