Jet, I agree with you about orbitals being a waste at least at the early stages. But once the players advance into big army's, then orbitals will be needed.

Because they are not just additional atk/def points, they serve as a way to hit more targets. Because planet can only hit 1 target per round. So in a way you could bring only 50 dreds and like 200 battleships. The battle ships could serve as a means of decoy targets for a planet to waste it's power.
But then I'm not sure how the AI works. If it set to attack strongest ships, than my strategy above is a fail.