https://www.youtube.com/watch?v=SVik5lWB0W0
DRK will be really interesting to play in 5.0
You have 2 strong abilities you want to play around to spend MP on that are oGCD, then you have blood gauge based skills that could potentially generate MP and then all the rest which helps with mp generation. On top of that you have something that War has "inner realese" which makes quietus and blood spiller free cost with each hit generating MP, not to mention a shadow which cost blood gauge which mimics your moves.
The changes are really nice and you will find DRK more interesting to play around managing 2 resources, which will be quite tricky because DRK will have so many options to regen them you will have to plan your rotation in order to not gain too much.
No DRK wont be slow at all, you will have 7 oGCD to use frequently, which grants different effects, 2 of them being those 2 strong abilities you want to spam all the time.
There will be a place for many rotations on this job.