The AI is slow because each one keeps it's own entity list, data for where to build etc etc. They don't share, so an 8 qBot game will be 7x slower than a 1 qBot game. Various components in it too could be sped up, like the AI finding what to harvest (i.e. is it reachable), where to build, among other things. And path finding has been getting slower as more things get added to the game. Philip is already working on the path finder, but I don't know when it'll be finished.