Glad to know the DPS taunt is a viable option in Nightmare still, but what is giving us problems isn't the taunt and switch or damage to the tanks. It's still the shield phase and transitions before and after it.
We messed around in 8 man NiM to test out strats and execution and my god, 8 man is a walk in the park. The bosses and mobs tickle. The DPS check is not nearly as demanding as well. I'm glad to see there is finally a tough challenge!
We killed it using the DPS taunt so it means that it works :P Shield phase is definitely the hardest part of the entire fight and requires everyone to be paying attention and killing the right things.