Would probably help if there were some reference videos from the jp side or anywhere really.
Here is a quite good one imo:
youtu.be/DmhmLPwa93E
Takeaways:
1. Build a defensive party with enough ATK down and healing, Jeanne, Cybele and Zephyr are key charas here.
2. Same as Inb4whales said, hold back firepower at beginning to accumulate burst gauge.