You can't go over 39%... Am I missing something, or is this a good idea? (Inb4 "penetration mastery" jokes) Oops didn't really mean to put this in gameplay & balance...gotta love these glitchy forums...but I guess this works
You're missing the fact that penetration from masteries is stacking multiplicatively with items, not additively.
Meaning, with both 3 points of the mastery and Last Whisper, they effectively have 0.65 * 0.94 = 0.611 = 61.1% of their armor. Meaning, you penetrate 38.9% of their Armor.
Wait, where does it say you can't go over 39% pen? O-o
I don't remember reading this anywhere... >.>
There is no cap, if you're reading wiki it's referring to maximum through items that you can get.
Like others have said, armor penetration stacks multiplicativly.
If you have 50% + 50% armor penetration, you get 75% armor penetration. The first 50% penetrates 50% of the targets armor. The second 50% penetrates 50% of the target's remaining armor.
As for the graphical user display showing 39% or 39% regardless of a 1 point mastery difference - the graphic user display in most games rounds information. Seeing as runes (and per level stats) go down to thousandths (or previously 4 decimal places in Sion's AD scaling), it's safe to assume attribute bonuses that go into decimal places are indeed factored into formulas.
