Jan 13th 2010 7:00PM Dreyja, I suspect that the Warcraft universe is Blizzard's place where they get to say "there is no absolute good, and there is no absolute evil".
On the other hand, the Diablo universe is where Blizzard gets to say "now this there, this is absolute evil". That might imply an absolute good. Maybe. But if you're looking for absolutes in Blizzard lore, that's the place to go.