fire mages got a pretty big buff for 4.3. So I might be trying that out.

BGs, I don't know. have to see. 85 pvp is pretty brutal. Have to practice on what to do when you get swarmed by melees. Can't be constantly losing slaves in a fight. Once split, the grouping up is pretty frustrating. If things get worse, I might swap a mage with a priest. Old school priest + 4 mages.

as for heroics , I am sure mages can do some.