I've seen quite a few tanks die from the tankbuster (Crush Helm). I noticed that before this hits the tank usually has a (cleansable) stacked debuff (up to 4*) on him. Haven't check yet what that was, but a friend told that this is a Vuln-up debuff. Using Esuna has unfortunately gotten out of favor by a lot healers I've seen in the last few months, maybe this was the reason you died ? When I'm running this with my BRD I usually use Wardens Paeon, Natures Minne and Palisade (when it's not on CD) on the tank.