You're probably right about the first part Governor.
The idea about making few changes at a time has cons and pros, one of the main cons is that balance can more easily be analyzed if all obviously needed changes are made at once because each time you change one thing it affects the other.
I hear SC2 gets changed frequently, at least that's what a friend told me (don't play it myself).
afaik SC2 doesn't have updates that change the gameplay frequently.
Most updates are about bugs or improvments of Client and interface and stuff like that.
For gameplaychanging stuff there will be the bigger Patches coming rarely.