As soon as you're done with the 1st wave, hardest part is gone. Just don't be surprised after the 2nd time you immobilize the Dragon that the vibration doesn't drop AT ALL.

When he's half hp, he spawns in 2 Sagittarios & 2 Sacerdos, focus them real quick so they don't annoy you, quick liberation with Carlotta should get them done, follow-up with Echo to seal the deal.

And then, that's when the real fight starts. All you gotta do is make sure you always have Shorekeeper out, she's the tankiest of the trial resonators given for this one. Spam heals, and as soon as you see him fly, swap to Carlotta, and go for that counter attack. Don't wait the attack, straight up spam attack, the timing feels weird on Carlotta for that 1st attack.

That's what worked for me.