The strat I use hasnt failed us.
4 melee, all either dual wield or MNK, all have Utsu
WHM/BLM (for escape afterwards lol)
RDM/WHM
WHM and RDM each stand on one set of stairs about halfway up. Melee each pick a corner of the floor. The Melee are in 'teams' based on which set of stairs they are in front of. Each mage focuses on the Melee 'team' that is in front of their stairs.
The melee teams stick to their sides and kill off the mobs that pop there. Once their side mobs are done, they can go over and help the other 2 melee. The melee each pick a corner. The imps that pop each corner are that persons responsibility. Imps die first no matter how many fomor are up. Help your teammate with their imp once yours is dead. Do that for every wave and you wont have problems.
For the NM. Bring 1 WAR or 1 DRK/NIN and its guaranteed kill. Have all 4 melee save tp off the first rounds of fomor. WAR 2hr or DRK Souleater Rampage and 3 other Melee WS the NM. With only one WAR we usually get it down to about 30%-40% on the first pop. Next time NM comes you will have items and you can 2hr again, but even with just regular WS's and a nuke or 2 from the RDM (if needed) will kill it.
The one time we brought 2 WAR was the time we got it to below 10% on the first NM pop. Any combination of 3 WAR or DRK/NIN should be able to kill it in one go.