The idea is playing keep away with the barb and peck at him with HoY until serenity cooldown is up. Engage him on a fresh serenity... and make sure you pop it (timing is everything here) before he rends. If it's done before the rend, watch him eat his own pain. If it's popped after he rends... it doesn't seem to do anything. I got this idea when i was playing around with my DH against Draco and he made me eat my own impale a couple of times.
Anyways, if anyone is more geared towards this set up and would like to test or would like to offer optimization ideas ... it's appreciated.
*edit* For better or worse, i used a skorn with this.