Boss Damage Vs. Ignore Defense Rate.

It isn't impossible, really.

Assuming "ignoreDEF" is an array of values, you can calculate it like so.

Code:

float physicalDEF() {
        float k = 1.0f;
        if(ignoreDEF.empty())
            return mobPDR;
        else {
            for(auto& i : ignoreDEF) //for every value in your ignoreDEF array.
                k *= (i/100); // k *= (i/100) is equivalent to k = k * (i/100) where i is the current value in ignoreDEF array.
            return mobPDR*k; //mobPDR * k is your physical DEF attribute.
        }
    }

Shouldn't it be k *= (1-i/100)?