Of all the areas that Dark Knight currently needs assistance with, this bothers me the most aesthetically. Dark Passenger is the most iconic Dark Knight attack in Final Fantasy (aside from maybe Night Sword).

Most of our actions are taken up with the twirly draw-a-line-in-the-sand Blackest Night, the awkward Climhazzard looking leap of Souleater, or of course the oh so spammable Dark Arts. Dark Passenger used to be a quintessential darkness attack that would add that essential element to keep Dark Knight from just being a flippy blade spinner. Not being able to use it in area or boss situations does more damage to Dark Knight being Dark Knight than just the lack of an extra off GCD.

Sorry, Cecil...