So recently I've been seeing how Blizzard is pretty much ignoring the shit out of Hellfire. I can only assume it is because of them not being the developer on the game, but it feels pretty weak imho. I think it was Eidos who was credited for making the expansion, and it was a really fun and really good expansion!
But on the the subject, a lot of things happened in the expansion that I'm not sure if it counts as canon lore. Not only does the last boss play a major role in the big scheme of hell and heaven, but the whole inect-y things and all the characters that are introduced, are those also ignored by Blizzard?
Nope, definitely not canon. Blizz didn't support even the idea of Multiplayer for Hellfire, that pretty much speaks for all. It sure had some cool editions ( and some lame aswell ) but it's not a canon, sorry.