Heavensward DRK whilst very fun will not see a comeback unless there is another overhaul of tanks in general, the reliance on being hit for low blows, reprisal and blood price meant it was MT or bust for optimization which is something the devs are very clear is something they do not want (although I think it should be what they pursue in general). SB DRK was the natural progression of trying to move MT reliance on HW drk, by taking the apm that would have been spent on the reflection actions and clunking it into one skill. Scourge was a casualty of the other dev goal of removing non combo dots from all classes as a way to save buttons and also make debuff management more reasonable on 24 man+ bosses (In HW it was a regular occurance that the "soft cap" was met for debuffs applied to a boss meaning you could not see the debuffs that you applied). And finally the MP drain was changed partly due to accessibility, and also partly because it didn't really mean anything, running out of mana only happened if you werent paying attention same way you overcapped on mana in SB if you weren't paying attention, sure you were punished more in HW, but honestly you were at way more risk of overcapping more often than you ever were at running out in HW.
So whilst many would like HW drk to come back, it would involve the devs walking back on multiple broad changes that effected a lot of jobs not just DRK, DRK was just caught in the unfortunate ven diagram of all of them.