Fast level 47-5X

Basically, there's a set of "arena" type quests in Tanaris, they're pretty fast and quite good experience. However, you get 4k experience per kill for the bosses (At 47.) With heirloom gear they arent even a challenge for most classes, you might have a bit of difficulty as a healer, not entirely sure.

You get the first quest at level 47 from "Dr. Dealwell" - He's at 51.8, 28.1 inside of Gadgetzan. As soon as the quest starts, walk inside of the arena and after ~5-10 seconds the boss will spawn. Kill it, abandon the quest, re-accept it. This works out at about 4,000 experience in 30 seconds - 1 minute if you're not slacking. Works out to 240,000 experience an hour, which obviously you won't need as you'll outlevel the mob by then.

I don't know what level it stops giving experience, or becomes bad experience per hour, but I know for a fact you can atleast get to 50 with it as that's currently what i'm at and still getting good experience. Will edit once I outlevel this method, might take a while as I'm on a pvp realm and there's about 3 level 90's inside the arena just killing everyone.

Might not be worth the effort of travelling to Tanaris if you have other decent ways of leveling or don't hate dungeons as I do, but it's pretty nice to mindlessly level at a fast pace.