I’d like aspir and drain on dark knight, but the way I’m imagining it would involve a pretty full on rework. It would also involve deleting the loathsome stalwart soul which is just a benefit really.

At its core would be
(Abyssal) drain gcd costs mp to give you hp.
(Quietus) aspir costs blood to give mp.
Unleash costs posssibly mp possibly a delay of a couple of turns of being damaged and generates blood. (They’re great big spikes, surely this would cause some blood loss)
All of this would be per enemy hit, but hp would be as a portion of damage dealt because it’s not the single target rotation. It also means there’s a tank that doesn’t have the same 1-2 pbaoe 5y radius aoe combo.

I don’t actually think they can take nascent effect off warrior at this point, or at least not without adding something even less healthy as compensation. It’s pretty easy to forget just how bad the average person is. Healers having a comical maximum throughput and tanks being largely unkillable with a bit of effort means a terrible support doesn’t end a dungeon run before it begins, but it also means anyone remotely competent invalidates the existence of their non-red counterpart.