The animation absolutely needs to come back; it was one of the most satisfying GCDs to hit in the entire game from an aesthetic standpoint.

In the absence of a drastic overhaul to DRK's entire toolkit, I think that bringing back Scourge would at least put a reasonable dent in the performance deficit DRK is currently in, as long as it's actually Scourge, the 1-GCD non-combo DoT, and not a cut-rate Goring Blade combo finisher.

It wouldn't fit into 4.x DRK's toolkit nearly as cleanly as it did in 3.x, given the addition of Bloodspiller, but it wouldn't necessarily need to.