Mages were still the top DPSers in my guild when we were raiding Uldar last week (I quit WoW since then tho, 24hour raiding for like 5 days kinda finished me off). A well geared DK was the only thing that could match them, however the mages are aggro magnets and need hand of salvation often if they are really pushing the tank.
TBH, all classes can do insane DPS if you play them right. Our raid leader is always top 3 dps as a shadow priest, but thats because in AOE fights he DoTs absolutly everything while he nukes the main target, he was pulling 7-8k DPS on Sartharion (in full t7.5 gear) when the whelps were spawning.
Hunter is probably the most challenging\hardwork\perfect rotation needed\etc class to play imo, but because of that also the most fun.
I would pick the DPS you like playing more to take to endgame raiding, although I would say that hunters and enhancment shamans seem to be in short order on our server.
Given equal gear, I would say there is easily 1-3k dps difference between someone playing their class to the max and someone that is just along for the ride (Uldar gearwise anyway) regardless of class.