When you release a AAA title, the third in a much loved series, after a twelve year hiatus, you want to get it right. When you're catering to a legion of adoring fans who have lapped up the months of hype and PR, who, shall we say, have perhaps developed a slightly over-evolved sense of entitlement, you want to get it absolutely right.
Knowing their fanbase probably a stumble. I hope blizzard appreciate just how loyal their fans are - it's impressive.