Quote Originally Posted by comicshorse View Post
So the Norse gods aren't gods, or the early Greek ones or indeed any Pantheon whose legends have an apocalypse as part of them ( or the Forgotten Realms gods while we're at it). Gods dying is pretty common
Not for the Judeo-Christian God. It doesn't matter what we, IRL, think. What matters is what the people who are considered 'experts' on the subject think. Magnus and Ahriman, the two characters in a position to know such things, both agree that there are no Gods. This is the metaphysics of the setting.

Quote Originally Posted by Voidhawk View Post
What we've run into here is a massive philosophical Question-with-a-capital-Q: "What is a God?". Or perhaps more usefully: "What do we mean when the word "God" is used?"
We use the term as the setting applies it. Which is apparently the JC God that is all-knowing, all-powerful, unkillable. And the Chaos Gods are none of those three things, and neither is the Emperor.