Did a bit of testing and found that if you cast Eye of Kilrogg and move the eye to a boss and stand on top of it with the eye, the boss will agro and come after you. I was with some friends in Kara and noticed that when I was standing at the entrance and used the Eye to look at Moroes he and his adds killed the eye and started running for us and brought all of their friends with them (all of the adds from both rooms near him) I also tested this in Stonecore and a few other places. As long as you are in an instance it should work.
Happy griefing