Developer credibility is irrelevant. The game is what you judge against. What developers say when they discuss how they think about the game in the future or why they have done something isn't black and white. Nothing really is. It's all gradations of grey with different points of view presented as a summary.
Thinking about design evolves. Saying that developers have no credibility is a great argument for developers to point at and then say nothing at all. This entire argument about what developers promise and whether they have any credibility is immediately solved by what's in the game. You like it or you don't. You buy it or you don't.
I don't know of anyone at all that avoids a game they genuinely enjoy because a developer said something about it that never came to be quite true.
Your signature signals better than anything what you think of Blizzard. And that's fine. But it also means that it's unlikely that you'll view anything in a more-or-less objective way. That's fine too. But this belief that developers need to only speak truth about future events is sophist*.
*http://www.dictionary.com/browse/sophism