I've been testing some class mods out in this latest campaign, including Rifleman & Engineer - both of which I like quite a bit & have become staples in my lineup - so I'm gonna give some honest feedback here. I had high hopes for the Assassin class b/c of the potential of a mobile stealth sniper, but the way the skill tree is set up doesn't really allow for it & kinda forces you to be a weaker version of either of the classes instead of a unique hybrid:

1) As a sniper starting w/ Phantom, this class is absolutely BEGGING for early access to Shadowstrike - or what's the point of taking Conceal - but doesn't have it AT ALL, and it doesn't really need Shadowstep b/c it shouldn't be at the front lines like a Ranger (it'll only be using the sword when it's guaranteed to finish someone off or they draw in too close).

2) Instead, it's a sniper that has fewer aim bonuses, but still has one of the worst abilities: Deadeye, something it can't afford w/o stacking aim bonus items (which you don't wanna have to use on your sniper class).

3) I noticed right away the Assassin is crippled as a sniper until he gets Snapshot (great skill to include), so I can't use a sniper rifle until he gets it, especially on time sensitive missions, otherwise he's just a sword running around w/o a gun, always setting up for a shot while the rest of the squad is moving on. This might be different if he had some version of Shadowstrike, so at least he was hitting hard w/ those opening shots from concealment (a niche worth filling w/ this archetype).

4) The 2nd tree should probably have more focus on using stealth, but as a sword-using sniper he could really use Bladestorm as a last line of defense.

5) As for Shadow Dash & Shadow Veil, I like the inclusion of passives, but +5 mobility is A LOT (my Ranger got this from AWC and she's a monster) - especially coupled w/ the GTS bonus - while +10 Dodge is not a lot at all, so it's not even a contest. The class doesn't really benefit that much from a little extra dodge (or even Shadowstep) anyway b/c it's not primarily a frontline Ranger, it would be better off w/ some aim bonuses. If for some bizarre reason someone wanted a sword specialist, a Ranger w/ a mobility PCS & Untouchable is always a better option.

If I tried to design a balanced Assassin class, the early ranks would look more like:
Squadsight - Shadowstrike
Snapshot - Conceal
Death From Above - Blademaster
Aim - Bladestorm
Shadow Dash (+3 mobility, maybe an additional +1/+2 ONLY in concealment) - Deep Cover

This is closer to the Sniper/Ranger hybrid class I'd like to try. (Ranks could be switched around of course, like Blademaster & Conceal, but Snapshot should be earlier on the tree & you should still be able to take both Snapshot & Blademaster). This way you wouldn't be forced down one path or the other (so, just Sniper), you could focus on attacking from stealth while still keeping sniping viable, or sniper rifle aim/mobility, but you wouldn't have to give up as much from the sniper tree for your sword to be useful. You'd still have increased mobility (but not over the top), or the mobility/defensive/offensive synergy of Aim & Deep Cover, Sharpshooter & Ranger abilities that were made for each other. The only real loss to the class is Implacable, but you get potentially the same effect from Death from Above instead, and w/o Bladestorm the sword is almost superfluous unless you take Reaper.

Anyway, I like the idea, I think it IS workable and this is closer than some other versions out there, but b/c of the dynamics of mixing melee & long range the skills need to be more carefully configured than other combinations of primary & secondary weapons (I've seen at least one other version that is a complete mess). Giving this class access to a shotgun sort of defeats the purpose & takes away the need for making a balanced sniper. All feedback here is meant to be constructive & helpful, of course. And just for the record, I liked the colored icons.