I haven't killed him in over a year but he was quadding for up to 167 with around 18-20k hp back in jan-mar '12. He's definitely 1 groupable with a solid tank (any defensive/evasive warrior or a high level/well geared monk/pal/SK) and a cleric + spot healer and 3 melee/pet DPS if everyone's decently geared and close to 60. Use more people if you've got less ideal levels or classes available. It's not like there's any items riding on the fight though so don't be afraid to try it with a less-than-ideal group (assuming you have a cleric with you).
He is pretty much magic immune (unless this has been changed) so don't bother trying to slow him or get nukes off, just beat him down. Levitate and EB are a plus, especially on whoever is tanking and anyone trying to buff/heal while swimming in lava. Jack your FR up to reduce lava damage and spread regen around if it's available.
I'm happy to help tank/dps on my monk if I'm online, which, considering my playtime, is unlikely. I'd suggest getting in touch with Kental to tank it for you if you're not having luck elsewhere:
http://www.project1999.org/forums/sh...d.php?t=107406