See
here for discussion of off-type defence bug.
What you have to remember is that as presently documented, each defence type (including additions from off-type defence) is tracked separately through a combat round. If you wear down the armour with your mass drivers it doesn't affect the outcome when you fire beam weapons at the shields.
The bug is that the off-type bonus isn't degraded at a normal rate because apparently the degradation is applied to the original off-type defence value, not the added (square-rotted) value.
Now I see, you mean the defense should not pooled together as one but should be by types as well.
100 Beam Def, 20 Mass Def = 100BM / sqrt(100)+20MA=30MA /sqrt(100BM)+sqrt(20MA)=14MS and that should be the static maximum value for each round. Any decrease of defense should only decrease the value of the matching defense type.
The current formula subtracts the values from the original un-square rooted defense value instead of the calculated sqrt value. So it seems 3 beam attack will destroy the defense value of a 5 mass defense just as much as a 3 mass attack. BUT 3 beam attack have a GREATER CHANCE of doing bleed through damage to HP as the mass defense value is square rooted while the 3 mass attack will roll against the full value of the mass defense and have a MUCH LESS CHANCE of doing bleed through damage?
Is this correct?