What would you say about human players who intend to mass towers with multiple expos?
Build a lot of statues and research destroyed form. Then when you have a handful of statues, go close to the expansion. Turn a statue into a destroyer. Then use that destroyer to siphon mana from another statue. Turn the manaless statue into a destroyer and siphon another statue.
Continue until all your statues are destroyers, then attack his towers. You should destroy them all, then easily take down the expo.