I must be playing a different game o.o cause my lil support character does like nothing for melee dmg~ her staff hits are weak. (<- note staff as it is a mage weapon) and my warrior/thief guy does quite a bit of damage with bows and swords.
Now from my understanding you are upset about damage. of course if you build a battle mage using the same kinda weapons as your warrior.. the damage will be similar.
Try this! make a mage and give them a staff and not a dagger/sword.
Do also keep in mind if you truly hate how it works, the tool kit will let you edit things in game.
Hope it helps!