I've done it in trio post patch, major keys:
-blm with 150 INT and 291+ Dark Magic, the INT gets 5/tick out of each elemental debuff, the dark magic gets 8/tick off Bio II
-rdm/blm with 100+ INT (I don't think 150 is possible for rdm from reasonable gear) and 211+ dark magic
-Fast hitting melee with speed gear (nin/war, mnk/war, war/nin)
Melee wears full out speed gear, haste, dual wield enhancements, brutal earring, etc. Adding an asston of STR and attack will barely make any difference, but faster hits will.
Blm takes first wall's DoT, burn/shock/choke and Bio II. Drain and Tier I nukes as MP allows. After the first wall falls the blm takes the lone NW wall solo. DoT at all times is key for the solo blm, there won't be enough MP to go nuke crazy.
Rdm is haster for the melee on the first wall, can also melee and toss out tier I nukes. After first wall falls rdm and melee take the east route, rdm takes over DoT.
Rdm and melee should be about halfway through the next to last wall when the blm joins them, and the blm takes over DoT for the wall. Burn/Shock/Choke will overwrite the weaker versions on it by the rdm, but you'll have to wait for the rdm's bio to wear to reapply that. At the last wall the rdm takes off running for the rune at the 5 minute mark, after tossing out a fresh haste on the melee and refresh on the blm.
Bio II has a static duration of 120 seconds, which is :50 in game time. Elemental enfeebles last for 90 seconds, which is just over :37 game time when unresisted, and can get half duration from a partial resist. You can overwrite them before they wear, I would cast them every :35 by the game clock to make sure they never wore.