I don't understand your complain about rogue damage at all to be honest. I've finished the game with my main character being a rogue lonewolf, and my other one being a knight.
My rogue dealt way more damage than my knight until level 16 or so. Rogues attacks are 2 AP and he has the highest movement. I could walk across the battlefield killing pretty much any monsters in 2 backstab (4ap) and then walk to another target and kill him too in only 1 turn.
My only problem with rogues end game is that daggers damage doesn't scale up nearly as much as every other 1 hand weapon.