What you want to do is be more than 30 yards away from Nightbane's drop point (The skull) when he descends. His aggro resets when he shouts &quot;Now I'm going to teach you a lesson&quot; or some such, so during the moments after that he will be sensitive to proximity threat and heal threat.

I run up to shield slam him with heroic strike keyed, and if I have enough rage I throw a clap in. 

Part of the difficulty we're faced with is that as he descends we're still fighting skeletons. The effect from that combat going on draws his interest a bit. If those fighting the skeletons can keep that combat a good ways away from his landing, the main warrior tank might have a better shot at preventing him from heading over to one shot someone. 

We'll get better at it, glad I managed to avoid the fears. Near the end one snuck through and got me, but it was short lived so barely noticable. :)

One of our most impressive boss fights that I can recall, definitely hard fought.