Blizzard didn't tell you any such thing. They told you "pay for one year of WoW access, and you'll get a free copy of Diablo 3 when it's released, and guaranteed access to the MoP beta". That's it. Whether D3 releases tomorrow, June 1, or December 31, you will get:
1) one year of WoW access,
2) free D3, and
3) guaranteed access to the MoP beta.
Here, since you won't believe me, is the text straight from WoW's website:
(Source:
http://us.battle.net/wow/en/blog/3767193)
See? "when the game launches". "future announcements regarding the launch dates of these bonuses". That's all they ever claimed. And since we STILL don't have a release date for D3, you thinking you'd be playing it now is your mistake, not Blizzard's.
(This is, of course, putting aside the fact that for those people that would otherwise not be playing WoW any more, but that signed up for the annual pass just to get free D3, Blizzard is making those people pay $180 ($15 per month for one year) to get a free copy of a $60 game.)
So it's your own fault for assuming something that a simple check of Blizzard's website would show is completely untrue. No one is to blame here but you.