Secondary Weapon Nebbing: Boss % or PDR?

Another 30%PDR line would give you a 10% increase in DPS against a 100%PDR boss, and for a 70%PDR boss it will be about 6.38% (it's a reasonably linear scale, give take 1%).

40%Boss gives you 15.6% increase in DPS, and 30%Boss gives you 11.7% increase in DPS (it's a perfectly linear relationship).

Hadriel