Did you play DRK on HW? DRK get the worst expansion transition with stormblood by far, on HW DRK use dark arts a lot too but never was between almost every skill like now since dark arts was more deep and fun and never cause the double weaving problems the job suffers right now, so it's really a bad desing bcs cause more problems that solutions.
It's not the highest HPS tank at all, WAR is it, storm path, equilibrium, inner beast, thrill of battle, I will love to see how you think sole survivor and grit soul eater can compete against that or clemency.
And no DRK is second on DPS barely over PLD on certain turns in alphascape, and it's even under 300 DPS compared to WAR on others, only in AS12 DRK is top.
Living dead is terrible compared to holmgang and hallowed, it's imposible combine the 15s of sole survivor with the 10 seconds of walking dead in practice and even that you will die since the 20% (not 30% bcs you need kill the target for that) inst enough to save you from the debuff bcs it's going to kill you if you don't heal the same amount of you Max HP, you depend complety on you healers to use this skill and don't die.
Inner beast and shelltron with the same ratio, I will grant you both are mitigation and no a shield but every tank have something comparable and it's the overall mitigation kit that's will matter, not just call for certain skill and say is fine, DRK kit is terrible until you get TBN since how baddly desing that on stormblood removing dark dance, foresight, and cutting the self heals make leveling DRK akward and unfun apart of other things like the blood gauge.
The desing philosophy and how do his role compared to the other 2 are two different things, on HW DRK have this same desing philosophy but with much much better flow, sinergy and special traits to bring to the party like reprisal and old int down from delirium, this is a mess, a barely working mess and the performance of DRK on raids can't be say it's well desinged and do a great work, the job do his duty in raw numbers but have triple flaws and punish you mistakes much more harder, offering less to the party for much more work compared to PLD and WAR thanks to the role skills that take what makes DRK unique and the mechanics around those skills.
Keep in mind DRK was by far the most popular tank job in HW with lot of downs on Alexander despite WAR being OP and now it's barely played on SB, you can like it and be happy but it's no longer the true DRK we get on HW and it's normal ppl complaint about it.