Just did this fight 3 times. 2 were my orbs and 1 was a friend's.
Setup was PLD/WAR, RDM/BLM, SMN/WHM, BLM/WHM, BLM/WHM, MNK/NIN.
I would just like to say, Spiro the MNK on Valefor is one hella DD, he was tanking half the time.
Buffed with Earthen Ward and Noctoshield. Buffing process took about 3min with resting. First BLM ES+Sleepga II at start, PLD vokes/Flash Cuu (WHM), it ended up buffing with stoneskin, so we had to smack it a few times and stack a bunch of DoTs to wake it up and pull it away from the rest. Also buffed a few other yags, everything was dispelled though.
Pulled WHM to the end of the black stone material to start area, beat him down, naturally used Benediction between 20-50% (Almost killed it once without it using it ><) and it was about when Benediction was used that some of the mobs would wake up, they weren't even near Benediction too. BLMs switched off Sleeping. One would stun BLM when it woke up and casting stuff.
BLMs Aspir'd Zuu (BLM) for mp, RDM did too. Next was Gii (BRD) which we also pulled from the others in case of song AoE buffs. BRD would actually 2hr very early, at like 80% or even higher. Killed without much trouble.
Moved onto SAM as opposed to BLM so the BLM and RDM could continue casting Aspir. SAM would 2hr high up too, at about 65-75%. Wasn't much trouble because it would use Yag WS which are pretty weak.
Moved onto BLM, stunned -ga spells and AM, sometimes slept too. Died quick, Manafonted at about 40%, didn't matter much since it would just Bio II or something. It did have a habit of using Sleepga spells though, only saw after Manafont.
We moved onto MNK, we didn't DoT MNK. DD were unlocked vs. MNK, and MNK was Stun > Bound > Slept and we all took the time to rest, PLD could Flash/Voke and still rest to near full. After that it was simple, SMN would buff again.
Moved onto NIN, once it didn't even use 2hr. However, even with Barfira it did 1009 DMG to PLD. Only had 1 death in first run because SMN was too close, and BLM last run dropped to 11 HP, though third run it did 700-ish to PLD. Point is: Mijin Gakure is deadly, if you have a BRD, Fire Carol the NIN. However, Mijin Gakure actually kills the NIN, unlike most NIN 2hr mobs (yay!).
BC over, ****** drops all around.
Hope this helps someone.