I never took the mech shrinker; I believed a small help in bullet avoiding wasn't worth some hp. I also very rarely take the "X% chance avoid damage" levelup option. If the mech shrinker also reduce damages, I will
never take it (even less than never...
). Maybe it's because I'm playing below my personal challenging level of difficulty, but small dodge helpers aren't worth a currency that can buy me more firepower. (I don't even consider the health/dodge survival-for-survival trade, just health as currency.)
Just my bits of thoughts.