First of all, basically all the responses above.

Second of all:
- what fight?
- what difficulty?
- how experienced (Personal and members)?
- actual one-shot (like Ramuh's Stratospear -> Judgment Bolt doing 999,999) or you stand in areas taking multiple damage instances?

Addendum, dying in a fight isn't a shame and not something you are supposed to feel bad about, it's supposed to be a teaching mechanism that hits harder than just giving you a -50% DMG down or a +25% vuln up.

If certain things didn't just outright kill you, you'd just learn to min-max of how to not die to them, regardless of how much of a ball-ache it is to tanks and healers shielding you if you aren't exactly shielding yourself instead of just learning how to do things right over time.