Flawless micro is an enormous, essentially insurmountable advantage, if backed up by even a modestly capable "strategic" engine. Even the world's best starcraft 1 pros make many micro mistakes over the course of the game--I'm talking blunders so bad that even I notice them. This is because a human cannot be everywhere at once, while an AI can. Take all the "mistakes" away and what you have is something that is nearly unbeatable without doing some sort of cheesy all-in strategy that gets lucky.

I think the true test of a Starcraft AI would be one with human-like restrictions. E.g., only so many actions allowed per minute, only vision of the current screen, built-in delays for actions that would tie up a human to perform, etc. Then the contest is truly more about intelligence and less about brute force.