Okay, so what gear were you using on each character?
I honestly did it a while ago but my main team I think was this:
Simon: Zirantian Claw, Ancient Glove, Ardan Helm, Lustplate, Givini pin.
Nalili: Durge sword, Tormented Shield, Erosian Dress/Naked Apron/Assault armor, and charm of great lust or succubus pin.
Vhala: Desert longbow, assault shield/helm, sanctity plate, and ring of strength or barrier pin.
Carina: Crusader Staff, Rune shield, Red Hat, Dwarven Armor, and barrier pin.
I think when Vhala ran out of mana I swapped in Hilstara and Qum to replace Carina and Vhala maybe? I don't remember it clearly tbh but I do remember the ruins being tough but not quite as grueling as the last 5 bosses in the hardmode Prison or the tower depths.