How to fix last whisper and void staff elegantly for non-ADCs

Make percentage penetration apply after flat penetration. In season 3, the way the math works was changed to the way it is now, which promotes building percent penetration against people with low resistances. At the time, the public figured who were into math (think Cloth5 style websites) were freaking out about how this would break the game.

Let's compare using the two separate systems. How it is now, void staff+ sorc boots vs 45 mr: (45 x .65) - (15) = 14.25 remaining mr How it is now, void staff + sorc shoes vs 200 mr: (200 x .65) - (15) = 115 remaining mr

How it was, void staff + sorc sneakers vs 45 mr: (45 - 15) x (.65) = 19.5 remaining mr How it was, void staff + sorc footgear vs 200 mr: (200 - 15) x (.65) = 120.25 remaining mr

With the new system, building void staff with sorc flip-flops will result in a squishy target having 27% less mr than it did with the old system. With the new system, buulding void staff with sorc slippers will result in a tanky target having 4.3% less mr than it did with the old system.

Conclusion: the old system of calculation better matches the expectation that percent penetration is a good purchase against tanky targets, and a bad purchase against squishy targets.

Note: this will affect ADCs very little, as most of them do not build any flat penetration.