I cannot stress enough how easy this is. Did this lastnight with a few friends and a few strangers.
75 NIN/WAR (me)
75 MNK/NIN
75 THF/NIN
75 THF/NIN
75 RDM/WHM !
The RDM didn't have BLM sub. We'd thought it may be a problem cause he didn't have sleepga, but you can easily get past this as long as everyone knows which one they are going to fight. We'd do a little layout and say which number we wanted.
1 2 3
4 5 6
It was quite easy and we did it really fast. The RDM just kept one slept as everyone solo'd their own and beat down until the last one was dead. Just be sure everyone names their numbers if they are strangers in the beginning of each run so no one forgets. Better safe than sorry I say. :P