Being a mage in DM

Ok I note that I used DM to denote deadmines, and that bothers people. But if you can run my lvl 21 mage through Dire Maul, I will give you 20g.

That being said, I suck at being a mage. We were in deadmines and we had a warrior, healadin, elem shaman, hunter, and me. Well we were all really too high for the instance (all 20's). I really wanted to just get some greens to DE, and I wanted to practice grouping with my mage. Firstly, I was dropping BOMBS in that place. As a fire mage, I really bring the heat on anyone I target. However I found that the group as a whole, typically killed off folks before I could get in 2 fireballs. Now on the boss fights I was amazing. I threw out pyroblast then 2 fireball, then another pyroblast. This dropped the bosses life really fast. The tank was good at holding aggro, but a terrible tank aside from that. He tanked well and all, but he would pull 2 or 3 at a time instead of one and letting me sheep one of the two. So when things got bad, they got REAL bad. I tried doing flamestrike (aoe on the ground with fire), but he'd move off of it ( he must've thought it was from the defias guys). In the end fireball, pyroblast, and arcane missiles were my big spells. I will try to get a group in stockades but, I am thinking maybe to just forget the mage altogether and just delete her.