I read in a previous post that it is pointless to research Starship defenses as they are currently not working at all. In that thread there was talk about simply using very small or tiny ships with the best weapon and having fleets of them. This would actualy be better than 2 or 3 HUGE ships vrs 8 tiny, The 3 can only kill, 3 ships while all the smaller ships get to fire (at least once) on the first round.
With defenses NOT working, fleets of smaller ships is far more effective than larger ships with defenses.