Tank IDENTITY

[Shurrikhan]

As you might have guessed, I also think that vampiric holy magic is an equally bad design decision,

But healing-bundled-on-offense is not inherently "vampiric". You're literally just taking one particular name for the mechanic and conflating it any and all attachable theme.

and largely comes down to the fact that if one tank has something, everyone wants it, and the dev team tends to indulge these demands to try to please everyone even at the cost of job identity.

...Like?

You could say the same for mitigation in general. You could say the same for discrete healing options-at-cost (which DRK once had via DA-AD, too). You could say the same for %healing taken increases (for which WAR had the highest total effect and average effect over time, but PLD had the strongest ability). You could say the same for flat current-and-maximum-HP increases. You could say the same for RNG-based mitigation (PLD built itself around it, then DRK). Even pure, flat shiel-- wait, no, no one else took anything like TBN to run with it.

So what is it about just self-healing bundled to certain attacks that's so wrong if it steps out of DRK's narrow box?

Thrill of Battle is just a kinder version of Last Stand. It thematically fits, and there's no damage to HP conversion involved. You're just increasing your capacity to shrug off damage. I also think that Wolverine style regeneration is fine for Berserker types as well. There's just no logical explanation for why a pure physical attacker should be able to use magical barriers or lifesteal.

While I'm no fan of barriers on WAR, per se, there is such a thing as physical damage-absorbing effects. They're just representations of the difference between "I can take a hit," and "I can take a hit so solidly I stifle its minor incoming status effect." That's the sole "not even going to flinch" element on Warrior; and you'll note they're pretty minor: a 400p shield on the EW upgrade to the on-demand, and on a raidwide for which they (overly, imo) favored parity over identity.

And sustaining oneself off adrenaline per Warrior's core theme is no more "vampiric" than is Second Wind.

There have been a couple of iterations of DRK which have specifically involved life steal, most notably FFT, which was the inspiration for PLD's Stasis Sword type spells, and FFXI, where Dread Spikes converted damage taken into HP. You don't need to go into an undead theme to do it (although they seem to have done this anyways with Living Dead).

Right, but 1-2 abilities like healing on Blood Weapon or via Dread Spikes do not in themselves make a necessary theme (nor were they, for that matter, chosen for this DRK), let alone necessitate that the job be the sole possessor of some capacity, chopping past and future job design at the knees wherever they may overlap.

Multiple jobs can be allowed self-healing, even on attacks. They needn't be nearly so thematically limited as you make out.