This. What Ren said.
When looking at any job producing sustain, Enmity, or any other secondary output (i.e., anything that doesn't, in itself, cause the fight to eventually end -- which in XIV's case is only ever damage), you need to consider the intended difficulty of the content and, given that, what additional primary output (in XIV's case, damage -- though it'd be net HP generated in a heal-boss-to-X% HP fight, etc. if XIV every had any) that can be produced because of those secondary outputs.
If the devs decide that they want the fight to, even at 100% hyperoptimal play, take at least 7 minutes to clear at minimum ilvl... it hasn't taken longer because tanks deal less damage while DPS deal more, but simply because that's the amount of HP they decided to give the fight relative to what DPS any party, as a whole, can theoretically produce.
All that will have happened is that they've given tanks deeper swing in how much offense they can trade to Enmity or sustain (damage nullification + effective healing done)... or have pigeon-holed their total contribution more towards sustain or Enmity.
By all means, insist on tanks and healers not being pigeonholed too deeply into secondary outputs so they aren't eye-tearingly painful to level solo, but tanks and healers not doing nearly DPS-level damage atop their secondary outputs is an indicator of at least decent role-balance, rather than a reason content would have been made harder.
Said content is, again, tuned around the whole party's damage anyways. Those dynamics just affect the relationship between roles and the balance of secondary to primary outputs normal in their gameplay. They do not affect the total output; only tuning changes ultimately do that.
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All that being said, Enmity (or "threat", "aggro", etc.) is just a ridiculously shallow and bloated concept insofar as we've seen it used in XIV. It's literally just been a "Price is Right" mechanic wherein one guesses how much damage your top Damage-Dealer will produce over the fight and how badly they'll fail to use their aggro-reducing abilities (if they have any), and you ride out tank stance until you've exceeded that guessed-at amount by as little as possible, and then drop it for the rest of the fight.
And then it took up to 7 buttons (Savage Blade, Rage of Halone, Shield Oath, Sword Oath [to get back from Shield Oath], Provoke, Shirk, and Flash [though at least that one doubled as mitigation with diminishing returns]) just to support that shallow crap? Hard pass.
I'd be interested in a return to Enmity management only if it were replaced with something with actual available nuance, like mob script manipulation, Focus (like Enmity, but determining only the next special attack and built up more or less independently in just the brief time prior to the attack, such that a tank could force formerly "random-target" attacks to itself instead of a DPS or healer), etc., and wasn't just a simple tabled value that sees no interaction outside of being halved by certain actions.
Even then, I'd spend only one discrete button on it: either Provoke revamped to carry additional effects, or the tanks' respective <Tank Stance> keys, revamped to be capable of instant or near-instant aggro that would quickly fade unless sufficiently followed up on. Let positioning and timing handle the rest.