Seeing PLD's rework I have faith DRK can have nice things too, so I will try to express those nice things here as far as my opinion of having played the job goes.

Current bloodgauge is a copy of Warrior's. I'd like to see something like this to make it different:
-> Gaining blood works the same it does now. With 75 you can do a 3 ability combo ( each attack costing 25 blood ) which starts with Bloodspiller. ( similar to RDM ) Bloodspiller would need to be changed to AoE and have a fall off. Quietus can be removed as it doesn't seem to be that flashy, maybe add 2 new abilities which are beautiful and flashy but for DRK, like PLD got its Blade of Faith combo. Or older abilities like Scourge, getting the PLD Goring Blade treatment.
-> Using Delirium grants 3 stacks allowing the execution of Bloodgauge actions without cost. So you can do this combo twice if you wanted during burst. One time from your gained blood, and one time from Delirium.

DRK's healing is lacking both in on demand (ex: Equilibrium) and rotationally (ex: PLD's Confiteur Combo, GNB's Aurora)
-> Remove the MP cost from TBN, add 5 seconds to its CD, but Dark Arts makes the next Edge / Flood heal you for potency equal to damage dealt. You use Edge of Shadow when you are about to maximize on MP normally, so this would help a bit, and you use it in dungeons a lot. This would solve the rotational healing issue. Alternatively, Dark Arts can just grant a flat potency heal when using the next Edge or Flood if specific values are desired for rotational healing.
-> Sole Survivor can come back under a form like this maybe:
"Marks targeted enemy and all nearby enemies with Abyssal Drain status.
Abyssal Drain: Attacks dealt to this target will heal the DRK who applied this mark over time."

Basically, if everyone from the party is attacking the DRK gets healed. Works in dungeons and in raids.

DRK has too many mitigation buttons that try to accomplish the same thing: Dark Mind and Oblation. No other tank has to weave 4 defensives to accomplish what others can with 2. ( 30% + TBN + Oblation + Dark Mind vs 30% + Heart of Corondum )
-> Merge them into the same ability. Oblation could grant 20% magic damage reduction with a further 10% against all damage types. The CD can be kept the same, or lowered to 45 seconds per charge.

Living Shadow is a fire and forget ability which acts similarly to a DoT.
-> Instead it can give you stacks of "Enhanced Darkside", increasing your damage by a further 20% on top of Darkside's passive 10%. These stacks can be displayed next to the Fray red icon instead of the duration, or along with the duration. You can get a cool visual effect like Fray is enveloping your character.