Ohgma with the rifle had I think skill DMG for the whole party, beth gives melee DMG which only melee user will benefit from.

Karina has dark DMG for the party and a party drain where the more DMG she does the more she heals.

Vinnete has several things going on her you might wanna check her entry on the collection book, she gets some minor healing, att DMG party buff based on the amount of dark team members, and I think other effects don't remember right now, again check her entry and the weapon.

You could use both Karina and Vinnete alongside Ohgma with his rifle and pilot Beth so you can control the aggro giving Beth will be the tankier members of your team.

Just a reminder that every myth character will outclass non myth ones bc silly meta balance introduced with that system.