(If you know what the Shard of Brilliance is, and you know how to get to the Veil from where you get it, you know all 4 quests are done) :P
We completed the run in 8 hours and 35 minutes. We nearly lost our monk at the exact same spot we lost our ranger last time, and we think it has to do with too many objects being left on the ground (after about half an hour in the place, no one picks up white and blue items). We had to have the monk drop out (disconnect himself) and reconnect while we picked up every crappy white item in radar range and deleted it.
Still, it was a very worthwhile and fulfilling experience. I am sure others will come and do this whole thing in 5 hours or less. but for now, it feels good to be the first group to have successfully completed this.
Other than the extra drops from the chests, there is no bonus towards fighting Mallyx himself. i.e. you do not get to fight him right away or skip the hordes that attack the priest before the Citadel door opens. In fact, you need to go back to the Gate of Anguish and speak with the priest to advance the quest.
Special thanks to the crew: Sal, Spardas, Hawks, Victor, Miriel, C and Fable. Also special thanks to the guys who have been helping me figure this out. They know who they are. Josh, Sky, Slim Shady and Kier to name a few.