I have found a abusive strategy, that IMHO, sould be disabled.
You make frigates withouth engines, make it good anty fighters, and with some good anti-capital-ships weapons, probably with multiple-head rockets and stuff.
Place a lot of these frigates in the same spot, much like a zergball.
Since the defense area of all these ships protect each another, anything that get near is anhilate. I have managed to win 100% vs 14% in missions that before was almost imposible.