Dex doesn't change the bow dmg as seen on the bow. It changes the dmg you do with that very bow. How else would you explain me criting a foe 35k+ with a bow rated at 156/268 dmg?
I've never played an archer but either you meant 3.5k or I'm missing something huge. With 100 INT and maxed Way of the Battlemage the highest damage my mage has ever done is 8k or so with a Fireball. My warrior about half that with a Rush Attack.
