I use focus for my spell targeting... so what i do is same idea. numpad 1 mage 1 has /assist focus numpad 2 mage 2 has /assist focus numpad 3 mage 3 has /assist focus... numpad 4 sheeps... so now i just use my /cast [target=focustarget] Fireball to dps down my paladins target. Long as you never lose your target on your noob toons you're golden.