Well, about Scourge, just returning the skill as it was during HW would not be that interesting within the kit. Yet, that doesn't mean we can't do something interesting with a non-combo GCD dot. And the idea for this already exist in the game and could bring back something Lyth talked about and that we lost too after HW : procs. Let me post an example, which require me to create two skill, one which we will call Scourge for nostalgia sake, and another one we will call Deep Cut (I was out of inspiration).

Scourge
Delivers an attack with a potency of X.
Additional Effect: Damage over time
Potency: X
Duration: 15s
Aditional effect : 50% chance to grant bloodthirst when damage over time is dealt by scourge.
Bloodthirst : Reset the recast time of Deep Cut.
This weaponskill does not share a recast timer with any other actions. (recast time, 30s, GCD)

Deep Cut :
Deliver an attack with a potency of X.
Recast time : 30s (off GCD)

It's basically how Bloodletter works on BRD under Mage's Balad. It would incentive players to maintain the dot on cooldown thanks to it having a direct effect with the procs, and it would also give us an oGCD which would be back regularly to break the current downtime of DRK rotation. And well, it's not thematically out of nowhere since we used to have procs back in HW with low blow and old reprisal. Putting the recast time of the dot on 30sec is to avoid having all the procs always on buffs windows, and not being a full uptime dot is to force downtimes even if we're lucky with procs. The only "downside" would be that damage would be more RNG based, with lower lows and higher highs depending on our luck.

If we want to further integrate those skils to the kit, we can add an effect to Deep cut, like a slight HP regen, or, depending on how it could be potencially reworked, an effect on Darkside.

Well, it's just some idea, and yeah, it would not be unique to DRK given it's also on Bard, but it would be unique among tanks, and it's not thematically off from some aspects of the historic and original playstyle of the job contrary to ShB Delirium, to take the exemple of another skill directly inspired by one already existing on another job.