Cutter's Cry

[Xenos74]

For the myrmidon princess, usually an easy way to kite the adds is to Stone 1 the marshal to slow him down with heavy, then divine seal regen the tank and yourself. The other smaller ants will pop soon, at that point just sprint the outer perimeter of the room and the princess should go down before things get out of hand.

Now the sandworm, he does spit a sand tornado at 1 person every so often. It inflicts a poison that should get cleansed with esuna but a regen would also suffice (optimally I would do esuna+regen). Any additional dmg your party took is really on them and not your fault. When the worm burrows, people can usually dodge his attack by seeing where he was going. The only unavoidable dmg is when he whirlpools the sand in the center and pulls everyone in....at which point you want to run out of the center before he surfaces

As for the final boss there...there's a bit of a learning curve for first timers and he's pretty harsh for healers. Hopefully you get a more attentive team for this boss because from your posts, there's no way they would have cleared it without an overgeared and experienced healer.