So who wins this battle?

I'm new to playing DRK, however, I loved WAR pre-SB. As WAR I could easily sustain much longer than I ever have been able to on DRK.

I was in the Castle Dungeon and on the second boss, the Samurai that spawns clones, we all got killed...EXCEPT a random WAR tank. The boss was at roughly 30% HP and the WAR solo'ed him the rest of the way. I've never seen a WAR or DRK do this like him. The WAR never fell below 50% HP! I never asked him how he did it, and the ONLY thing he said throughout the entire dungeon was "I really miss Bloodbath.."

I was always told that DRK is the self healing tank. While PAL is a mit tank, and WAR was high health and dps. I did notice that the WAR had on all STR gear, with STR mareria..

Can anyone tell me how he pulled this off? Is DRK able to do this? Who's better at self sustain?