Anecdotally, I have had 20 point defense medium ships take full damage against 6 missile attack small ships. If it is working, defenses are not worth their mass in bcs.

I think they are working but at very poor efficiency, like you need 3 to 1 or more to not take damage.  My first game I went very heavy on defensive ships and was running ships 2 sizes larger.  If I attacked a single ship I took no damage but if I attacked a fleet of 3 I lost my ship and killed one of their's.  Loosing a 100 hp ship to 3 20 hp ships made me balance out my ships.  I didn't see much difference in results and just started using fleets, still lost ships at at ridiculous rate but slightly slower and by that time I was pumping out ships fast enough that it didn't really matter and I quickly mopped up the computer.

So the conclusion that defenses aren't worth the mass is is right.  To get enough defense to really make a difference you hardly have any weapons, let alone sensors and life support.

Thanks for the reply Mormegil!

I know in GC II if I had (10) defense and I was facing a (5) dmg weapon of same type {using generic here} I would not take damage or rarely did. Here at GC III it seems that the defenses do not work that way at all. Now it (feels) like I need 3 defense points to nullify 1 attack point. This really feels wrong and goes against years of play from GC II but may be what your folks vision is. 

I will wait till the combat is actually in the game before I get concerned. 

For now Ill stick to multitudes of tiny ships with a single weapons and no defenses.