Now, I'm rather new to the game, so I haven't had many in game battles, as of yet, but it occures to me to wonder, is defense actually of value with the current system.
My thoughts are this: if a defensive module weighs roughly the same as an offensive module of the same type (so far most of the defense modules have been heavier), then a 4-0 offense-defense ship takes roughly the same fitting as a 2-2 offense-defense ship, and according to the simulator, they're pretty much equal in performance, so long as the defense rating is the appropriate defense against your offensive weapon. If the defense is even split, the battle is almost always a cleen sweep for the pure offense ship.
This implies to me, that any race that specializes in a single weapon, to the complete exclution of any defensive technologies will have an advantage over any race that splits its research to train defenses as well, s they will have ot train, not only offensive tech, but as much as three separate defensive technologies as well, leaving the pure offense race with a defacto tech advantage.
Those of you who played Eve may recognise this as the "gankageddon" scenario.
Harry Voyager
Addendum: A possible solution (if the issue exists) occured to me after I posted this. Basically, instead of a swrt penalty to off-type defense, grant a 50% bonus to on-type defense, thus the 2-2 becomes a 2-3 when facing an offense of its defense type. Thus a race that researches both an offense and a defense will have andvantage over one that doesn't.