Maybe the Deviator should be allowed to attack air. Anyway Deviators are fun, whether you know how to use it properly or not. But it's always nice to observe the route your enemy always takes to come to your base. Then plant some Deviators on the way, and put some Kobras and AA Troopers there for defense. When he attacks, just send his units back or destroy them. But you need alot of Deviators. They're quite cheap, though.