I agree with the above poster.. you should level up a healer. Really, more a rezzer. You'll have a mage die frequently enough to want one.

Levelling up my mages I actually didn't have a problem in most instances pre TBC, as long as my mages were the same level as the mobs. Before that level, you just have too many resists to play effectively. Usually I could kill most mobs before they got to me.