Facing Healer DPS goes well into dampening where you can finally land a kill.
I am an average player but still I don't ever remember it being this hard to land a kill as Unholy. Scourge strike hits for nothing.
And I don't think it's just me either, facing Unholy's in arena as a healer seems like a game where you don't have to stay on your toes much and feels much more relaxing to heal through than something like rogues, ferals or most classes.
Yeah, it feels like Unholy's ''threat'' is completely gone. In Cata and MoP you had to be careful and not let him stack necrotics too high or else you'd be in deep shit, now you just use some instant heals and you're fine.