No, I'm referring more to the fact that there aren't even enough Novice water spells in the game to allow you to fill out the maximum 6 skill slots which you can learn. Not really any choice there when you have 5 spells to choose from to fill out 6 slots. One should probably be moved down from Adept to Novice.
I say, make Guerilla trigger from from Invis/ShadowWalk /Sneak. For balance tweak, get noticed that 2 Scoundrel's status related skills have 150% dmg. IMHO That is not correct. So nerf these Scoundrel's 2 attacks skill(s) a bit. Minus 15%? That way general damage would be similar but bursting promoted.
I don't see any justification for a nerf like that. Guerrilla is supposed to be more the Rogue's thing. Those 150% damage skills have significant cooldowns anyway. You can't do them every turn.
About decaying touch, I was thinking you shouldn't nerf it because I thought the decaying touch was a smart move against ennemies that heal themselves with potions (I'm thinking about Grutidla, the orc leader in hunter egde). But it's maybe too OP, so you modification is maybe needed aswell.
I don't think Decaying Touch needs a nerf. It's a short range debuff spell with a short duration which only does something if A) the AI randomly picks that target to heal and not anyone else, or B) If you choose to burn one of your own healing spells on them, leaving them unavailable for yourself.
And if the fight is already easy enough that burning a healing spell to knock out a single enemy makes it easy enough to not be able to need the spell on yourself, then the problem is with something else, not Decaying Touch.
