Along the walls of this dungeon, you will occasionally find Magitek Photocells. To spawn the first two bosses, you will need four of these Photocells by the time you reach each boss.
Once you have four Magitek Photocells, click on the Magitek Terminal to spawn the first boss, an ochu named Coeurl O' Nine Tails. This boss will frequently inflict poison on any nearby party members, so unless you're the tank or a melee DPS, stand back.
While the healer can remove the poison with Esuna, it applies it so often that I recommend just healing through it. Once the boss is downed, touch the Magitek Terminal once again to open up the path.
Round two with this Ochu! The fight will start off similar, so stand back if you can to avoid poison. At 50%, two small Ochu named Warden's Whip will spawn at what appears to be a random location in the room.
About the same time, the boss will start to inflict slow on nearby targets as well. As the tank will have to move near the healer to pick up the small ochu, it's likely the healer will get hit with slow. Quickly Esuna it off and move away, as it greatly impacts cast speeds. If you have time, also remove it off party members, though the tank will take fairly heavy damage while the adds are out.
When Graffias is pulled, Fleshy Pods will spawn around the edges of the room. While you can leave these up, we found it helpful to use spend a little time using instant attacks to clear them all out at the start of the fight to create more room to move later in the fight.
With that out of the way, Graffias will occasionally use Silkscreen, a frontal attack that the tank needs to step sideways out of. If you are hit by it, you will take damage and be knocked backwards. If the fleshy pods are still up, this can inflict quite a bit of unneeded damage onto the tank. Two scorpions will also spawn, which should be quickly picked up and become the DPS priority.
While the tank is dealing with the adds and the knockback, Graffias will cast Sticky Web on a random party member, spawning a Fleshy Pod at their location. Once all members have moved away, use a ranged attack on it to prevent them from filling up the room.
At 50%, Graffias will cast Tail Molt, exposing his tail as a new target and enabling him to use the ability Deadly Thrust. This will create an extremely large green puddle on the ground, which the tank should move out of quickly. DPS should focus down the tail to disable this attack before the room becomes too full with puddles.