I main a hunter and out of the other classes that I have played I would recommend to you Shadow Priest or Boomkin. While you have to remain stationary to cast some spells, you would be surprised how mobile most ranged classes are. Even as a hunter it's not like you are running back and forth constantly as you cast your abilities. Not to mention Shadow priest and Boomkin are just a blast to play.
I have played a mage as well, but I don't find them to be as mobile or partcularly fun. Some people love mages though so to each their own