Some notes, purely my opinion, but thats what comes to my mind at least right now. If i misunderstood something about design then please explain it, since ideas are awesome:

Energy Steal - should probably change it to something like "Reduces weaponskill recast time and auto-attack delay by 6%" unless direct stat influencing is by design

Steal - I dont really either see the reason for it to have several positional skills. You mostly will sit behind the enemy for stealing, since potion and grenade are pretty much useless. Why would you use a heal instead of 7% if healers are not dead. Not even 500 potency, like second wind. I dont see the reason to use Grenade either, 200 potency is nothing compared to 7% damage up you get from stealing from behind (on single target that is, which currently is 90% of high end content). And since you will run around the boss for mechanics a lot, you will just either need to find a moment to use steal from behind to actually benefit from steal, or just use true north and dont bother.
Probably something like GW2 steal would work better in this scenario. You steal, get random effect. Although to make potion and grenade more viable, they would need to have some damage bonus as well (like potion 400 pot heal and 4% damage up, grenade 200 potency and 3% damage up).

Flash Powder doesnt need stun. Singletarget stun that is. Aoe stun would be one thing, but here i feel like giving blind effect to the enemy would make more sense (at least if blind still affects enemies [or bosses lul]).

Aoe combo is being cone -> circle is a bit weird but i guess it works. Although Soul Swipes on 64 is a bit too high for second aoe skill (yeah dragoons get it 61-70 range too, but they dont get any mechanic that pushes blood of the dragon beyond jumping and more st combo skills until later on). Ninja gets its second aoe hit at 52, which does exactly the same thing as soul swipes. Better if it goes down to 50-60 range too.

Escape Plan - interesting idea, but for it to be usable you will need to do pretty much 2 mudras before excecuting, bit too much for a disengage. If its just used when you need to disengage for boss, idk if using 2 abilities -> disengage gonna be easier then just running away. Both abilities are melee ranged as well, so to be able to use disengage successfully, you will need to know beforehand that such situation will occur. Also if its used as emergency, player will most likely just clip gcd to use it, instead of using gcd and running away normally.

Underheaded Tactics should be locked to battle, like everything else in the game (anatman, meditate, aetherflow). Otherwise parse runs will most likely just start with sitting 2 minutes waiting for it to go off cd

I would unify Stealth effect names into one. Some skills give you "Obfuscation", some give "X stacks of stealth". Not like its a huge problem, but it does cause issues when trying to understand what skill does (at least for me)