Balance, Homogenisation and Encounter Design: The Problem.

[linay]

enter homogenisation, the systematic removal of anything that isn't 'damage', and the death of job identity.

If job identity causes one tank to deliberately sacrifice all but 1 hp, then let it die.

Otherwise, this tank uses a gunblade, that tank uses a sword and shield. This ranged DPS shoots arrows, that ranged DPS dances. This caster summons egis, that caster attacks from near and far. All these melee DPS use positionals differently.

Those differences are sufficient for job identity.