At higher levels, if you want a grind party, 1 fighter, 1 cleric, 3 mages IS the dream party. I've heard it being stated by many people. That's if you want a maximum-capability grinding party, and it's easy to see why it would be considered a "dream grinding party."
Increasing the damage on a mage, as an archer, I think would unbalance. If you increase mage damage, just watch the number of archers complain on the official forums. We're already broken BECAUSE mages take our role. They stole our DoTs, they have high damage, they have great AoE. Mages become extremely impressive once they become high leveled, and we don't need "impressive" turning into "overpowered."