The DRK Consolidated Feedback thread has strayed from its original purpose, in my eyes.
My intention is to suggest realistic and feasible changes that fits DRK back into what I see as its intended niche: The Middle Child, more offensively oriented than PLD, but with more/stronger defensive options than WAR.

Broad Strokes Changes in regards to Balance
PLD brings a great deal to the table in terms of DPS output, mitigation, and raid utility. I wont beat a dead horse with the specifics, but the simplest means of balancing PLD's contribution to the tank meta is to lower its DPS.

WAR retains its traditionally high DPS, but Raw Intuition and Vengeance, two powerful defensive CDs, in combination with role skills have actually made it the most defensively oriented tank within the meta.

The simplest change would be to increase the cooldown on RI and Vengeance by 30/60s respectively. This puts WAR's CD rotation similar to DRK but less powerful than PLD.

DRK is currently the weakest tank in regards to the meter sticks of DPS, Mitigation, and Raid Utility, and requires a bit more in depth tweaking.

Suggested Changes(these are individual suggestions and combinations of any would require more specific balancing)

The Blackest Night: Decrease MP cost to 1200mp(1/2 Dark Arts), increase duration to 6-8s, other effects unchanged.

Adjusting the MP cost of TBN has a twofold effect: Increasing DPS output by decreasing PPC loss, and increasing general mitigation. The increase to duration is largely QoL.

Dark Mind: Change effect to "Reduces Damage taken by 10%, DA effect 20%.
This gives us a short, quickfire Rampart, which improves DRK mitigation above WAR, but still below PLD. One could argue that damage typing is an antiquated system and have a solid argument. Personally, I like it for utility on other jobs(ala feint/addle), but I don't think type specific mitgation has any business on a tank.

Shadow Wall: Reduce cooldown to 120s.
With the proposed Vengeance change, this gives DRK a defensive advantage over WAR while still letting PLD have the stronger CD suite.

Dark Passenger: Revert to Heavensward values, rework the skill entirely, or remove it.
This is a particular bugbear for a lot of DRK players, because the reasoning for changing it from HW is largely incomprehensible. Reducing button bloat by making it useless is like trying to lose weight by cutting off a limb: You're lighter but now you're handicapped.

These are, IMO, bare minimum and feasible adjustments to balance tanks and help give them more identity.

Quality of Life Changes:

Plunge: Increase range to 20y. Because other gap closers are 20y.
Blood Price: Increase Blood Price MP regen to HW levels until Level 66 "Enhanced Blackblood" to reduce the burden on low level DRK.
Sole Survivor: Grants 5 points of Blackblood every server tick for its duration, other effect unchanged. This makes Sole Survivor less niche and gives it a decent purpose.

Feel free to contribute, please try to keep changes minimal and balanced. Outrageous ideas are likely to be dismissed out of hand, as will anything that just puts DRK on top of the imbalance.