I don't know about Diablo 3, so this is more of a general answer.

If the content you ask about **is, or has been available to the general public** (usually through a public beta either through sign-ups, a paygate or even completely free and open for all) in a form that they could *play* the content, it's on-topic.

If the content has never been available to the public to play, it's off-topic.