so getting killed by Ureaus for casting cure 3 once after the tank had used most of his MP healing himself is normal yea?
Don't cast Cure III. Like ever. Sacrifice III if you must, but try to stick with Cure II. Also, Soughspeak and Chameleon is your friend.

Cure is 1 for 1 HP healed to threat gen. The exact same as damage. And you are going to be lavishing a crapton more HP back to the tank (Esp at Urasaeasreaseases) so going to need help. You would think that Provokes and the like would help compensate that, but they only go so far, I guess.