A lot of end instance bosses are REALLY hard to pull off with 5-boxes. I did drop Vazruden. Once. Decided it wasn't worth the trouble to try and farm any drops off the guy.

Other notable pains in the ass are The Blackstalker in under bog, the escorting Leeroy Thrallkins through Old Hillsbrad event, and Talon King Ikiss.

Having now gone through about half of the BC instances, I have to say the movement in fights now isn't so bad. The complete lack of forgiveness if you don't move exactly right is whats REALLY annoying.