Actually she says at Auchindoun, not in it.
And the point I was trying to get across is that immediately after you finish the instance and give the blade to Voss, Auchindoun is empty, there aren't a bunch of soul priests raising and TURNING the dead. Obviously, eventually more soul priests will come and go back to watching over the souls of the dead, but soul priests don't actively attempt to raise fallen souls for the hell of it, they just tend to wandering souls.
I don't know how you could possibly read Voss' quests as her slaughtering good draenei soul priests, or how anyone could read her as insane to begin with. It's quite clear that she has been using the soulblade to fight the actual necromancers of Draenor, like the shadowmoon orcs.