On the vampire quest. It's so hard!!! The group attacks are deadly by this point of the game. How to survive some fights, I don't know...
I got frustrated and started grinding instead of doing them. I just beat one of them like it was a joke.
Tiz/Ringabel/Edea:
Freelancer/Ninja (because Freelancer is the only job not capped)
Support Abilities are Comeback Kid, Axe Lore, and Dual Wield
Gear: Fox Tail x2, Heiki Helm, Heiki Armor, Barrier Shroud
Agnes:
Freelancer/WHM
Support Abilities are Silence Immunity, HP 10% Up, MDEF 10% Up, and Auto-Shell
Gear: Whatever gives you the most MND, and the Barrier Shroud for
Utsu+2 attacks for each DD. This gives them a chance to cast Utsu again before the next AoE.
Agnes either Defaults or Aerogas each turn. I like to keep her on the back burner in case I take a lot of damage. If you prefer all DD, you could probably easily get away with that and stick to items to heal. I am level 99, but I think that's sort of irrelevant when only 1 attack (a weak bite) got through on my DDs.