Early in Azuna, there is a quest at Azurewing Repose, to kill Ael'Yith. The quest is called Hunger's End.
Kill Orbyth fast and but dont kill Ael'Yith. Just tank him and wait for "Excess Power" adds to spawn. They give full XP of a mob, but are 1 shot. You get around 500k XP/hour.
You can drop the quest and do it again indefinitly. Have fun.