As a new source of lore, I was particularly displeased. The Varian Wrynn story seemed particularly silly. I understand both of him defeat Onyxia, which in addition to being an extremely contrived situation also means that she was not killed by a band of hearty, though obviously unnamed, adventurers.

I’ll have to somewhat disagree with you on the point that one does not need to be familiar with these sources to enjoy the core game. Varian Wyrnn, a character developed in the comic books, was basically dropped in many players laps at the start of the WOTLK without anyone knowing who in the light’s name he was. As a result, much of the reaction to him has been mixed, confused, or just outright negative. Nobody knew who the heck this goku-haired king was that held so much hatred for the orcs and had an antler headed night elf and scantly clad blood elf in his posse. Varian just came off as a completely alien ad brutish moron that wanted to destroy the peace so many other, more familiar characters had worked to uphold.

So, yes, I’m happy to have additional sources of lore, but they should be ancillary rather than necessary. They shouldn’t mark the beginning or ends of characters or stories that will become crucial to understanding the game’s core plot. The fact that the WoW comic is starting a plot involving the new guardian of tirisfal and the disappearance of Thrall further makes me even more uneasy.

I agree with snowleopard233.

Blizzard has clearly gotten much better with storytelling in Wrath. There's no reason to confine major, game-defining lore in a comic book... or a book for that matter. I'm fine with comic books and books elaborating on or detailing the lore, but hopefully we'll move away having to read such works (or their wiki summary) to have any clue what's going on.