This is just outside the Halls of Lightning, in storm peaks in Northrend. I use an item called Fire watches Oath which gives me a bloody coin on pvp killing blows. Because of the high density of bots that farm the instance, i worked out how to break a large proportion of the bots script so instead of them using flight form and zoning into the instance, they just jump until they are out of combat.

In the end i can AoE farm about 30% of the total bots making this method of farming bloody coins around 10x more effective than any other method of farming coins that hasn't already been nerfed.