Currently, Dark Knight struggles with having a mechanical identity. As a tank, it’s main defensive selling points are that it has a low cooldown anti-magic defensive and TBN can save low HP allies from damage more easily than other options, with the trade offs being that it has less tools for physical tank busters, has the weakest cooldown short cooldown for multi-hit tank busters, and its short cooldown defensive is a DPS loss if needed multiple times in a short window. Meanwhile, in terms of DPS, the job basically throws everything in the two minute window, then does little else but it’s basic combo and Bloodspiller in between bursts. And since Gunbreaker released, Dark Knight was rarely the highest DPS option, so it doesn’t even have that niche anymore.
On the gameplay feel end, to me at least, it feels like it became a Warrior with more burst phase oGCDs and worse defensives. There isn’t really any interactions between the abilities outside of TBN giving a pseudo-refund through a free Edge/Flood, which does at least have a neat optimization where you can squeeze in an extra Edge during burst phases. And while technically Dark Knight has two gauges to manage (Blood and MP), only MP has decision making tied to it.
So what I would like to see is the return of Heavensward Dark Arts. The Heavensward version had different effects based on what ability it enhanced, usually more damage but often also had a bonus effect. This style of Dark Arts would do a few key things for Dark Knight. First, it would allow Dark Knight to have an avenue for better defensives without needing more buttons. Dark Arts plus Dark Mind could say give blanket mitigation, Dark Arts plus Quietus could be a heal per target hit, Dark Arts plus TBN could give a heal/second shield, and so on. Second, it would allow its rotation to feel a bit more unique to other tanks, as you would be using an oGCD to empower another ability, tweaking the flow. Third, it would allow more flexibility in offensive and defensive cooldowns based around triggering Dark Arts effects.
And for me, the biggest thing it would do is give Dark Knight a very interesting mechanical identity, where they can trade damage for protection and vice versa. Currently, of the tanks, onlt Paladin really has big trade off abilities in the form of Clemency and Passage of Arms, one which trades offensive MP use for healing and the other which is a channel that doesn’t do damage. A Heavensward style Dark Arts would allow Dark Knight to have a more extreme version of that, which would fix a lot of pain points in certain content like dungeons and physical tank buster raids while not making them more powerful in Savage, as the extra tools come at a DPS cost.
Of note, I don’t necessarily want it identical to Heavensward’s version. It could be an oGCD or something like Eukrasia or a new kind of button. To me at least, this feels thematically fitting for the job.