Here's what worked for my group doing FL assaults:
Bloody Rondo - RNG/NINx4 BRD WHM
If you have hate, run, if not keep shooting. When he pops a clone, have your RNG WS and take it out. When you get turned into a bat, have your bard horde lullaby.
The Price is Right - SAM/WAR x4 MNK BRD
Meditate Twice, or sleep TP. When you hit 200+ TP, buff, have one of your SAM use Warding Circle, Warcry, and have the rest put on Berzerk. Soulvoice Double Minuet, Barparlyze, and go to town. Once your initial 200 TP is gone (Sekkanoki > Gekko > Gekko) Pop your 2HRS and Gekko him down. Bard will need to diaga weapons when they come down. He should be dead very fast.
Better Than One
PLD/NIN SAM/NIN x2 RDM/DRK WHM BRD/WHM
PLD (and SAM's, though not as critical) should have a barfire set. Melee should get fire carol/march, and barfira. After buffs, mages run to the upper right corner, PLD should engage and tank Black Shuck face to face. SAM should be on the side closest to the Mages:
X = Shuck
S = Samurai
P = Paladin
M = Mages
X S ~20 yalm~ M
X S ~20 yalm~ M
P
Have SAM's do a dark skill chain to MB Slow (2) and Elegy. RDM/DRK needs to keep an eye for Shuck to Howl, and be ready to stun its TP moves. If it spawns fire elementals, your Bard needs to be ready to cast a long spell (stoneskin, reraise, etc), and agro all the elementals as it runs by. Elementals will depop after 25% damage is done to black shuck after they popped. So your bard can reraise and sack again if needed. Other than that, its a straight forward fight.
The Susanoo Shuffle
PLD/NIN SAM SAM WHM BLM RDM/DRK
Don't remember what we did specifically with this one. I think it was just straight forward melee during the magic shield and vice versa.
Bellerophon's Bliss
PLD/NIN SAM SAM RDM/WHM WHM BRD/WHM
Endurance fight. Have PLD BRD WHM hold Khim while the SAM's and RDM dispose of the goblin. Once the goblin is down, everyone focus on Khim. The fight can get VERY bad towards the end when he gets below 25%, so you may want to have a mini zerg ready at 35%. The range for Fullmination is 30 yalms, so you may want to have your RDM or BRD sit at 31 just to paralyna your WHM then they can get everyone back up. Also Lightning Carol and Barthundara at 40% is very helpful.
Hope this helps your group.