I played DRK a lot in Endwalker, and really liked having to manage 2 gauges (MP and Blood). In Dawntrail I did the MSQ as this job so I could have the worst possible tanking experience in the new dungeons, in order to feel the thrill of surviving on this frankly underwhelming tank. But the changes to DRK made it more dull to play, you build up MP slower so you press your magic buttons less, and you no longer have to worry about overusing blood before your even minute bursts. Now I'm too scared to even use TBN, and while darkside now needs more careful mp usage, it's more boring than last expansion's gauge management.

I'm not going to repeat any improvements other posters have put forth, but I wonder if we could remove Edge of Shadow, but rework Flood to be one of those "Higher single target damage with aoe falloff" attacks. That would free DRK up to have one new attack, either an ogcd or an addition to our gcd combo.