I don't have dragoon, so I will not speak on how to play them. I do play White Mage as a main and you shouldn't be dying on primal fights. When I heal, I know the dragoon, and few other jobs, are glass cannons. I know I need to keep regen and stoneskin on them, and I do, to make sure they don't get one shotted. There is no reason for anyone to die on HF for ifrit, not even the dragoon. All four nails should be taken down, which is cake if you bring jobs, and your white mage should be keeping you at full life for the fight.

Sadly and happily, jobs require players to play with teamwork. If the White Mage slacks on his job, the dragoon suffers for it.