Soleron on 20 June 2012
They needed to see how players reacted to the game content and what strategies/builds were powerful, which could only come after release same as WoW and SC1/SC2/Warcraft. Developers can't think of everything nor are they good enough to know the best builds immediately.
Remember SC1 is the most balanced competitive game of all time (objectively), Blizzard are the best at this.
