i just stumbled upon Bonebreaker as well, I have Diablo and Griswold in the other rooms, so they have not been replaced. Does anyone know the setup for this new boss??
I got it from playphunsuk from my server.
Bonebreaker setup is:
mob - mob mob
mob - mob B
this boss is infantry, so plenty of time to shoot him down!
He gives more XP then Diablo, but less then Griswold.