Mages are very effective in DKS, especially if you duel wield weapons with magic damage bonuses and/or enchantments (no need to boost the Duel Wielding Expertise skill). Any magic damage bonuses get applied to each magic missile or other attack spell. Early in the game you can use magical weapons so you can concentrate on boosting Intelligence and still have the option to fall back on ranged or melee combat waiting for spell cooldown or mana recharge.

mages

Spell question

Battlemage build

New character help..

There was a mage guide for D2:ED (here), which might be helpful, though some skills have been modified, and other changes made in DKS.