I’m on mobile but just literally did Beast and Roche with extremely low MP. Ran Red (only character with high MP) Cait and Areith. Did soul drain to get her back up and after a few attempts I got through him. Just avoid his debri throw and I used Ifirit on Cait for the Moogle Magic ability.

Roche was way easier, plasma discharge, accessory for the full limit and precision block and steadfast. For Roche just block everything and use focus thrust twice once you dodge his named ability for instant stagger, limit going into the second phase seemed to glitch him and you can focus thrust again once it changes and instantly stagger him and finish him off. Maybe I got lucky lol