Level 38 warlock, affliction specced.  Sent in the void when he and his buddies were in a add free area, then put agony, syphon life, and corruption on him, then each of his friends, by the time I was finished with that, his had run out, and my void was low, so I healed him back to about 800 hp, then hit healthstone, reafflicted forzuk (his buddies were dead) and then kept draining life, maintaining the curses, and healing the void as necessary, life tapping when low on mana.  He went down no problem.  (I did die twice before finding this method, though one was due to an add)