Killed him last night with a group of 90-95. Merc healer 95, merc tank 95 IS sufficient, but an additional healer with good group heals is a must. A 91 pally with heal AA's and heal crits done is enough.
It will be tough if you don't have a player controlled tank or healer. The key to win the fight is to avoid/reduce the damage of AE DoT, but merc don't know to keep away from it.
Killed it with 95mnk, 95wiz, tank and healer merc in full burn mode.. very close though.
This guy can be a pain. Be ready to rez your tank if necessary, and have a second tank (a good pet works) to tank the mob in case the tank dies. Hits for a max 14k, and that combined with the dot can be ugly, even if you are in the 50K+ Hps. Be always on guard to heal the MA.