[capnq]

The first thing that comes to mind, which isn't displayed during combat, is ship experience, which gives a bonus to both attack and defense. That sounds very much like your opponent had a very experienced ship facing your fleet.

The second thing I see is that his ship is faster than your fighters. His ship's combat move is 4, your fighters can only do 3; they're never going to catch him if he's using a Maximum Firing Range strategy, unless you manage to "pin" him against the edge of the Tactical Combat screen.

I'd recommmend a new fighter design with a smaller weapon, more engines and/or Afterburners.