You can use backstabbing only with daggers. And daggers are dex-based, one-handed weapons.
Who gives a shit about backstabs when a normal hit from a 2h sword deals more damage? ^^
And yes, I know it costs more AP to use to but it also deals more then 50% additional damage on just an average hit. Then you have to factor in Guerilla which means it's (2+1)x 2 AP vs 4+1 AP. And then you need to account for positioning, Rogue has to be behind the target which means more AP spent repositioning.
And as I said earlier in this thread, even if Rogues are better at straight up sneak attacks alone warriors have the added utility of being able to take a few punches and unload huge AOE attacks.