That, in fact, is exactly what got me thinking that it's possible that BlizzCon itself is bad for the game, for the game community at large, and for the future of the franchise. BlizzCon, by its very nature, is a hype machine. It's where we learn details about the expansion - its name, its features, its setting and goals - before they are even close to being ready for players. People play demos. Developers give talks about the games. In many ways it's very exciting. I've never been myself, but most of my coworkers and a lot of my in-game friends have. So my argument isn't that BlizzCon itself is bad.
But looking over the past year or so, in terms of Warlords of Draenor and player interaction with it, I start to wonder if having the big reveal at the convention does more harm than good, overall. Expectations are set at the convention - looking at the recent player reaction to the news that Karabor and Bladespire wouldn't be capital cities in Draenor, the issue can in part be traced back to the fact that we were told they would be at BlizzCon. Players (like myself) had months to get excited about the idea of Karabor as a capital city. Then, suddenly, we were told (almost as an afterthought) that no, the capitals were moved to Ashran.
I want to be clear that I don't blame Blizzard or its developers for wanting to hype their games. For one thing, if you're having a giant convention you're sort of obligated to do something there. BlizzCon is a huge convention, it's not cheap to go to ($199 this year) and people expect a certain something for that. This to me is part of the problem - there's a sense that BlizzCon has to shock and impress us that seems to motivate talk that is less actual and more theoretical and those theoretical statements (what the company wants to be able to do) are taken as promises. Also, there's clearly a certain amount of excitement that sometimes gets ahead of people. Blizzard's development team seems very passionate about the game and their work, and that's all to the good - but sometimes passion talks a bit more than it should.
The three cases where I think BlizzCon has seriously hurt Warlords of Draenor (at least in terms of fan reception) are in the development of garrisons, the location of the faction capitals, and the nature of women being represented fairly in the expansion. In each case, it's not like much was even said - but the impact of BlizzCon on the fan community is immense. It hits the echo chamber like a bomb going off, and everything said at the convention is analyzed. Let's be completely fair and honest here - it was a huge mistake to answer a question about a female character's appearance in the expansion with an off-the-cuff 'boys trip' response. Combined with promotional materials that were of a group of orc dudes, it started off the expansion with a negative perception that it has never overcome. Many players simply decided they weren't going to play it, based entirely on the idea that it was a game made by people who didn't care about them or their voice being heard - an opinion started at BlizzCon. (I don't pretend that Blizzard hasn't had other problems in this regard.)
Similarly, the upset over the change in Karabor and Bladespire's status from faction capitals to glorified quest hubs comes entirely from the fact that Blizzard told us they would be faction capitals at BlizzCon. Horde players were excited for Bladespire, but many Alliance players literally salivated at the idea of getting to set their hearths to Karabor, a storied location in Warcraft's lore and the place infamous throughout Burning Crusade as the Black Temple. The way we found out we weren't getting Karabor as a faction capital was disheartening all on its own, but the reason so many of us even knew that it was ever going to be such a capital was the BlizzCon hype bomb. If Blizzard had never hyped this, we wouldn't be angry at having lost what we never had. I accept that it's silly for people to get angry about a fictional city in a video game not being a place they can keep their bank alt parked, but MMO's in general are silly places, and sometimes we simply have to cater to that.
Finally, the evolution of the Garrison has been fraught with player dissatisfaction almost from the very first. As Blizzard has iterated on the design they've backed away from some of the statements made at BlizzCon and afterwards - you no longer get to put your Garrison anywhere you want, for instance. It's understandable that these changes occur, but by painting a picture of the Garrison as one thing, you're always setting yourself up for disappointment when you don't achieve all of those goals.
What's the answer, then? Just don't have BlizzCon? That seems overly reductionist. The easiest solution would be to more carefully consider exactly how the expansion is hyped and presented to us. Whether we think reasonable, every statement made at BlizzCon is taken far, far more to heart than it could possibly be meant - we can talk about managing player expectations, but when Blizzard is the ones creating those expectations up on their own giant stage, there's no one else to blame when they start raging out of control. Saying less and delivering what is said needs to be a priority in the future.