So far, I find that of the current abilities that can be activated, an auto-cast would be overpowered.
Given that the AI controlling it's units is effectively the same as our units having auto-cast, why would making things even be overpowered?
For one, player versus player must be considered, as it's an integral part of the game (and arguably one that will strongly influence the game's longevity).
Secondly, the AI auto-casts, but it's still just an AI. It's highly limited compared to a player's adaptability, not to mention that its auto-casts are not always used intelligently and therefor mostly wasted.
Knowing WHEN and WHERE to use an ability is part of becoming skilled at the game. One less hurdle to worry means one less reason to feel superficial joy at accomplishing something in the game and one less factor that differentiates players of varied skill levels.
