As Horde, I've always gone into the mine. There's a lot of mobs in a dense area and as a Druid I can kill just as fast as my energy regens. But, I've probably killed a good 1,000-1,500 or so mobs in there with no luck though.
As Horde you don't need to worry about something jumping you if you AFK for awhile...Alliance can't farm in there.