Ignore def doesn't stack

I know that which ends up leaving the monster with 65% of their original def left, as you can see in the math I did 25*0.65 = 16.25% def leftover meaning I should have 83.75% of my range dmg, however with my range*total dmg boost*def reduction the lowest I should hit would be 38315

Your formula is wrong. It doesn't take away from it being 100%(100-35=65). It's 35% of the actual pdrate which is 25. So you would only ignore 8.75% of the pdrate with the current def ignore you have of 35%, not 16.25% like you say you should, atleast I always thought that's how def ignore worked.