These mobs give you 5k experience a kill, they are found around the coords 59, 22. They have around 20k health, and hit for 900 on clothies. I have been farming these for about 3 hours now and have gone from 74 to 75 in that time.
Here's a screenshot:
I died because I tried to aoe farm them :yuck: Being fire sucks for that. nonetheless you get alot of experience, and as these are quest mobs that are meant to be killed at around 90% hp, blizz did not intend for the to be soloable