Yeah, 80-85 is relatively fast. For sure you will want to go to each new zone as soon as you hit the right level for it. I think it's Deepholm at 82, Uldum at 83, and Twilight Highlands at 84. The experience boost from mobs and quests is pretty large from one zone to the next. So you can do a sort of 'fast track' by hitting each zone as soon as you ding, then if you want to finish the quests for any reason (like gold, or to unlock dailies) you can go back and finish them quicker at 85.