The difference here is that Blizzard's development staff aren't people you can just hire off the street to flip hamburgers who can be replaced on a whim. Nor are they individually responsible for stand-alone, critical chunks of the project. You have entire teams building those "chunks," and replacing an entire team with completely new people isn't going to get things done faster, especially in a skill-intensive industry that requires comporting to an artistic style AND working cohesively as a team.