You're a level 20 cnj. Your dps will mean very little and your party does not have the HP pool available to let them dip while you try to dot all the mobs and complete a dps rotation. Your priority is healing. If you are having to prioritize dps over healing then your other party members are undergeared for content or just completely clueless.

Why was the THM getting hit by ifrit's breath attack? I assume the tank was trying to help dps? Very bad idea. The tank does very little damage anyway and forcing dps to move to avoid attacks because ifrit got turned around actually lowers the dps on the nails the party could do. It sounds like this may be why your party could not dps the nails fast enough and not because you were doing your job, which is healing.