Tried it with three geared out guildies last night along with my ungeared Sentinel self. I just got demolished over and over. I would run to the sides during the Bulwark burst, but it seemed like after the burst channel was done and the animation finished there was still a delayed hit. It also seemed like there was another invisible AOE that happened even positioned behind him. I would interrupt his bulwark smash but that wasn't hurting me. Any suggestions from those who have run with undergeared marauders and sentinels?
Bulwark smash is what kills the tank so you must interrupt it even at the cost of your own life. It stuns the tank (who cannot get out of it even with their own anti-stun abilities) and, if it is not interrupted, goes on to deal around 10-14,000 damage to the tank in regular mode (I haven't tried it in hard mode yet).
The fight takes a lot of patience and focus, but you must protect your tank by interrupting the smash or you're going to wipe over and over again.