There is this spot in the Jade Forest zone, located in the temple of the jade serpent where there is a room that spawns
Water Fiends
. They spawn extremely fast and provide normal experience. They die very very quickly and you can farm hundreds of them in just a few minutes.

It works even better if you have a lvl 90 friend help killing them while you tag them all.

Here is a picture of the spot:



Enjoy!

PS: don't forget to use the
WoW
anniversary item for even more xp!