Could someone explain the Necros Reaver to me?

I was reading this thing's tooltips earlier and was rather...confused, at least on oblivion. The way I read it, Oblivion only works well if I go around and apply Necrosis, Looming Demise and Deathly Calling on every enemy before this skill can do...anything at all. Seems like a waste of time considering that most mobs drop in no time in aoe situations. Or, am I reading it wrong and all you need are the first two on the primary target and DC on everything else nearby? This wouldn't be so bad given Grave Rot, but we have no other way to AoE spread the other two.

So, can anyone explain this to me?

I meant the Revenant, by the way...but no one can explain this skill to me? Is it ever worth using over my Zealot? Seems more like the multimob raid dps mob to me.

Seems I goofed again, not Oblivion, Ruinination...

It's confusing, but my testing seems to dictate that you only need to have Necrosis and Looming Demise on the first target. However, all targets need to have stacks of Deathly Calling.