You probably won't get an answer on this, as games rarely give out exact drop rates, and people would just complain about numbers that haven't been used in 3 updates. But it would be nice to have more information. It took me a second to (i think) interpret your question. The question is if it's the base drop chance of exotics in general or per activity. I don't think there is a game wide base drop, so from my understanding is drop chance would work something like this Bc + (bc/2) + bp + bptm Where bc = base chance, bp = bright paragon and bptm = bright paragon stacking.