I believe the DEV said something like.. adding "Easy mode" and "Hard mode" for the primal fights later..
hopefully for dungeons too..

<imagination>

If people are rejecting a tank because he has no fire resistance gears, that will be at least a step closer to the "hard mode" in my imagination... (ie. Tank is going to die even with the best healer who keep on buffing, doesn't die themselves)

And of course.. 5% hp left after hellfire for 3 nails destroyed... with stoneskin + sang. rite + protect + sentinel..!!
(Ok tank maybe you can have 9% left but Ifrit can hit 8% of yours if the healers don't act instantly after hellfire damage)

</imagination>