After getting it to 80, farming a bit of the ex trials and the 80 Dungeons, its a much smoother experience comparative to SB DRK.
DRK now feels closer to DRK of the HW days (which I am personally a fan of). SB DRK was a bit clunky, it felt closer to a wannabe ninja/bard with its high APM and chaotic nature of MP regen. However, this made sense for the time because of the way Darkside and Dart arts worked together, but it was wonky and lacked flow regardless.
Shadowbringers Dark Knight has predictable mana gain with predictable Blood gain, which makes on the fly decisions with TBN and Edge/Flood much more impactful comparative to spamming Dark Arts all day every day. For example: expending your excess mana with Edge, but leaving just enough for an upcoming TBN usage/planning out your regen ticks makes you feel rewarded when the TBN pops for the Dark art Proc... Versus SB where it felt like trash using TBN to only give you back a GCD resource... that still wants to be enhanced with Unga Bunga Arts, it also gave a resource back that could overcap, which also felt awful.
Edge/Flood are fine, Mana gen is fine, the job without BW Haste is performing fine. SE did an excellent job of stream lining the job, while also leaving bits and pieces of optimization that FEEL impactful & noticeable. I feel those that enjoy a spammy active tank job will enjoy GNB more.
Delirium - Is fine as is. Can it be improved? Of course, but its function works and the 5x of 1 button is not awful design, its certainly better than just giving us more blood weapon w/a resource cost.
Bloodspiller/Quietus - They feel good to use & perform well, only improvement I'd suggest is to give them both 400 flat mana per use. Doing this would give delirium windows a free flood/edge, instead of current delirium which only gens half a mana spender with natural regen. Even if untouched it works well.
Abyssal Drain - Make the cure potency flat 1200 that can not be stacked with more enemies. Would be a gain 5 or less targets & Single targets, would prob give DRK the self sustain that it lacks compared to the other 3 tanks.
Salted Earth - Surprisingly works, but feels like its there to be removed for next expansion. Theres not much you can really add to it that wouldn't infringe on the current foundation of DRK. Its a button you press and forget about in single target, and does decent damage aoe. I'd only suggest that it gives HP back per tick per enemy maybe, but I cant really think of anything else. Suggestions in comments would be welcome.
TBN - Do not touch, fine the way it is and much better than SB incarnation.
BW - Good the way it is now, maybe reduce CD every 5 seconds with every BS/QS used like Warrior, but it might make them unbalanced compared to other tanks. If unchanged it will still be in a good spot regardless.
In summary: My feedback for Current DRK is keep it mostly unchanged, just give a couple QoL changes & it will be great. Have had about as much enjoyment with current incarnation as I had with HW DRK, I am also someone who hated Unga Bunga Knight back in SB. Its a great foundation to build upon, and it can only go up from here. Just my 2 cents.