Zealots/muta/dragoons/Hydralisks is just a standard rock/paper/scissors game theory thing, and it shouldn't be too hard to calculate an approximate nash equlibrium. The problem is that there is micro, macro, game theory, imperfect information, and an AI has to tie all these different aspects together (as well as perhaps some perceptual chunking to reduce the complexity) so its a real challange for combining different cognitive modules. This is too close to AGI for comfort IMO.