main issue with Dark Knight is fundmentally their kit more than any individual potency.

Giant shield they can put up.
Unkillable for 10 seconds.
Can jump in to the enemy from a great distance.
Can pull in and root other players.

Their entire job is to engage and catch. But this is all primarily designed with crystalline conflict in mind where such effects are much more manageable. Its a pvp job that makes me think of the old days of Warcraft during Wrath of the Lich King where the Death Knight class was nigh unkillable, had high damage and even had various buffs and debuffs as well.

And its just not just dark knight. With other jobs and their quirks, a lot of it revolves around what I suspect as the core design of "Wouldn't it be cool if..."