Try Dark Knight x2 and Alchemist x1. Equip all three with a Speed Bracer for Auto-Haste, then use Black Sky repeatedly with the Alchemist recovering HP/MP when needed

OR

Berserker x3 with Evade&Counter

OR

Gunner x1 with Catnip and Alchemist x1 for reviving. Dark Knight x1 can help out with Black Sky.