With My 4 mages & a priest at 55, I was clearing pulls in LBRS AOE style that most 70 mages would have trouble with. (I found out the hard way when I tried to do it yesterday with a 70 booster 4 lvl 50 druids healing).

The point is equally leveled mages have a great time AOE pulling stuff, to the point where I wouldnt recommend a 70 booster above say SM (At least not as a mage).