Our DPS is fine, TBN is fine, our opener and rotation are fine. All we need is some ability to restore our own HP, especially in dungeons.

Change Abyssal Drain to something like its old Dark Arts version. 3000MP, no cooldown, no MP restore. Same damage and cure potency it has now.

Change Oblation to provide a powerful HoT if the shield from TBN breaks on the same target, or if target has Walking Dead.

Change Walking Dead to provide a big lifesteal to all attacks for its duration. Decent DPS and the Oblation HoT should be enough for a DRK to heal their way through.