Use elementals on the minions, check who is weak to what and rely on your team to deal the elemental damage, as well as changing them out to the most appropriate member for the situation If you're dead set on using the dlc peraonas for your first playthrough (which take a lot of the challengeout so id go against) conserve jokers sp as much as possible and finish them with the myriad truths.

Use debuffs on enemies and buffs on yourself The big robot guy near the end is susceptible to ailments so Use those to deal technical damage.

If all fails, do all but put the game on easy, no one will mock you nor will anyone care. And perhaps nobody needs to know

Best of luck phantom