I would argue that a warrior who is sneaking is not much different from a Rogue, but you're right; 2H will deal more damage than Daggers when taking skills into account. This stems from the fact that Daggers are 1H weapons (and are Dex based) compared to the Str-based 2H weapons of the Warrior.
I'm fairly sure 2H will deal equivalent damage to daggers even without taking skills in to account.
Backstabs do get an increased chance to hit though compared to attacking from the side, which will lead to the enemy turning around less often. Good point, definitely an advantage for the rogue.
That, and attacking with Daggers uses less AP, which means that they can be more versatile with their attacks; it's much easier for a Rogue to hit-move-sneak than it is for a Warrior thanks to the AP cost difference. This in turn makes it easier for the Rogue to be in a good position in Sneak mode at end of turn so that the enemies don't attack.(2+1)*2 AP for 400 damage x2 (800 total) vs 4+1 AP for 800+ damage is a more or less realistic figure. There is advantages to both being able to sneak often and not having to. Also, if a Warrior can't resneak it's still a Warrior, what's the big deal? :P
Edit:
Actually, does Guerilla even work with Skills? From what I have seen it doesn't, since the characters exit sneak mode just prior to casting the skill (it says Sneak Failed), but my eyes could just be playing tricks on me. No, it doesn't.
But it works with normal attacks w/ any weapon. And the advantage of being able to sneak in to position at the start of battle and/or being able to resneak after unloading some big attacks remains the same.
