what is a Dark Knight? / to me, Dark Knight is a "physical melee Damager-tank that can use dark magic and blood magic." but, most of Dark Knights "magic" was removed, and made into what it is now. 3.x Dark Knight was best Dark Knight, and we need Dark Knight to go back in that direction, but as a different person said, "bringing back 3.x Dark Knight" does not mean copy-and-paste old Dark Knight. we need to take what 3.x Dark Knight was and "remaster" it into a new form that is like, but not is, the original Dark Knight.
How is Dark Knight unique? / no, no.. how "was" Dark Knight unique.
Dark Knight was a physical melee Damager-tank that could also use instant-cast Dark and Blood magic.
this is what Dark Knight should return to. Dark Knight should have physical GCDs and oGCD Dark and Blood magic. physical attacks and weave instant-cast magic between physical attacks. also, double weave. Dark Knight should have a lot of double weave, giving it a "fast" feeling, sort of like weaving both a oGCD physical attack, edge of shadow for this example, and either a Dark or Blood magic spell, between the GCDs.
and GCD should have variety. did you know that Dark Knight used to have two 1-2-3 combos, and one 1-2-3 Combo even had 2 different pick-one 3's to end the combo? Dark Knight needs to have this back, as well. GCD options, not just one damn straight-forward 1-2-3 combo.
What do we want to fix so they can feel like the class they should be? / the class that Dark Knight should be, is its original 3.x "identity", and Dark Knight should be half and half. combine 3.x Dark Knight things, bring back what we lost, and combine that with what current Dark Knight has. while, by "bring back what we lost", again.. not copy-and-paste. old skills that we lost should be remastered, all of 3.x Dark Knight should be remastered, into a similar, but new, form that can combine with current Dark Knight.
this is just a quick summary, though. I have a huge "re-Inventing Dark Knight" pet project that goes neck deep into re-Inventing and re-Designing Dark Knight in a way that is 3.x combined with current, in a way that I would like to believe would work.