Larian Studios Forums Divinity - Original Sin Divinity - Original Sin - General int and spell damage - capped?

Poison
Spore Barrage can be single target, though difficult to line-up properly
Ooze spray is aoe damage

Water
Winterblast is aoe damage
Wall of Ice is aoe (very small aoe) damage

Ultimately I recommend you equip your mages with buff/debuff spells like Wildfire and Blind. So even if they can't throw out damage, they can still contribute.