My fight with him tonight led me to this post.
We fought him tonight and ran into the same original issue. we tried everything and the only thing that would lighten the load for the rapid shot was LoS him. Other than that it seamed that he would pick a random target and unload.
I tried taunt numerous times and he would not respond. So no interrupt, no taunt, dead assassin... then dead heals, then me.
yep, tried it again this morning. same thing.
it wasnt like this before the patch, but he isnt even mentioned in the patch notes...