They would have been rolling with 8 defense against your mass drivers. I don't think any of your weapons had 8 attack or more, correct?
If so, then my initial thought is that the bug is still present, even if defense degradation is now happening. The degradation is being done to the initial 71 defense value, so the drath only started rolling with 7 defense after they took 7 damage. After that, it's another 14 points of damage before they reduce down to a defense roll of 6. This means that if you don't have any weapons that individually exceed that, you have to get VERY lucky roll to get damage through.
Thats just a guess, though, based on a single battle, which could have been just luck. Anyone else seeing stuff like this happening?
I actually saved the game just before this battle because I was tired of being slaughtered so I wanted to test it. I just ran the battle 5 more times and each time, same result. The amount of damage varies a bit but I never get more then 8 total damage on them.
Here are the details of the ships. I apologize, I only had 5 ships to the Drath's 2.
My fleet:
3 medium hull ships (31 hp, 31 hp, 7/31 hp). 21 attack (mass), 0 defense
2 large hull ships (66 hp each). 27 attack (mass), 2 defense (missle)
Drath fleet:
1 small hull ship, 10 hps. 16 attack (missle), 16 defense (missle)
1 medium hull ship, 23/27 hp. 255 attack (missle), 55 defense (missle)
Most battles have 8-11 shots on each side (both same amount).
My shots rarely do 1hp damage, mostly 0.
End of battle always results in all my ships dead, his medium hull ship with 5-8 hp damage and his small hull untouched.
Hope that helps.