Why is this so difficult to understand? If a character's attacks are doing 1000 damage before the DC is active, then this already includes Mothma's 90% reduction and Jabba's 30% reduction and whatever Krrsantan's defense is mitigating. So, now just take 75% off of the 1000 = 250. It really is that simple.
Let's look at armor shred for an example: each instance of armor shred reduces defense by 50%. So, a character with one armor shred is at 50% of their normal defense. The second armor shred does not reduce them to 0 defense. It takes 50% off of 50%, so they have 25% of their normal defense. The next AS reduces it to 12.5% of the normal defense. And so on.
Here's a second way of figuring the problem. Don't add the percentages off, multiply the remaining percentages. 90% off = 10% remaining (0.1). 75% off means 25% remaining (0.25). and 30% off means 70% remaining (0.7). Multiply 0.1 x 0.25 x 0.7 = 0.0175 or 1.75%. So, if an attack with no reductions would do 1,000 damage, then the attack after all of the percent reductions would do 17.5 damage. Yes, that is very low, but it is not 1 damage.
And it's not me "deciding for myself how the maths should work." There is a proper way these functions operate. I teach this to my students. CG has this one wrong. That is why it is a bug. It is programmed incorrectly.
It doesn't matter how you think it should work, just the way it does work. All stacking multipliers work that way in the game.
