This method is easiest done by an 85, but I was able to do it as a 79 DK. Make sure you have decent AoE.
In Burning Steppes, right outside Blackrock Stronghold, is 2 groups of 25 Humanoid mobs each. They are all grouped up, so DK can just lay DnD, hunter can Multi-Shot, whatever, and it should kill them within a second or two if you are 85.
Then, all you have to do is loot them.
To find more groups of them, just travel around the mountain that is directly south of the stronghold. The mobs you'll be killing are Blackrock Soldiers and Smolderthorn Assassins by the way. If this is a repost, sorry, delete.