Dark Knight has been a class which has historically centered around enfeeblement, sacrifice, and damage, it has been a kind of "hurt me I dare you" job. I could get behind this job as a tank because the idea of a tank which enfeebles enemies for defense (reprisal and delirium), steals resources (syphon strike and souleater), and has something of a counter attack system in low blow procs was appealing, fast, and the combination of it all felt good. There were some issues and things could have worked better, but nothing huge.
Stormblood rolls out and SE has decided to remove all of that and replace it with dark arts spam. While I enjoy actively hitting buttons, I have to agree with others that it does offer very little variation. What would I prefer as dark arts? First off I would prefer if dark arts was only spent by GCD actions. It would make the mini buffs feel a but more if you could dark arts, oGCD with a dark arts effect, and then hit your GCD action to consume your buff. I would also prefer systems which had some sort of interplay with the rest of our kit. Perhaps leave DA on Souleater as a damage and HP restore, make dark arts siphon strike a bleed which deals damage and restores mp/blackblood, and perhaps have a third GCD which has a dark arts effect which extends blood weapon/price or adds additional haste bonuses.
I also disagree that warrior and paladin are bland. Warrior is balancing its gauge spending with maintaining its crit buff while also spending as much gauge in buff windows as possible. Paladin is looking to abuse its utilities/defense to gain more shield swipes for damage. Both classes are also using GCD manipulation to end phases with more damage just like TBN. I think you are short changing the other tank jobs a little here. However, I do agree with you that complaining about how many buttons have to be pressed is probably a sign that you are playing the wrong job and another might be more appealing.