Originally Posted by Legacy Draxon
the problem with this is like shown above the armor pen stacking aready making armor useless. BC and LW give 70% arm pen combo that with runes and masteries your looking at maybe around 85-90% armor pen. to balence this issue we need to increase the cost to warmogs to 3k. and we also need armor pen after about 60% have diminishing returns so armor is once again viable. so you can get up to that 70-75% mark. but not with ease.
Your numbers are off. You're not accounting for multiplicative scaling, which reduces how much it actually affects. Here's how it works;
You have 100% Armor.
Black Cleaver removes 25% of that Armor. You now have 75% Armor.
Last Whisper ignores 35% of that Armor. You're being dealt damage as if at 48.75% (not 40%).
Further attempts to reduce/ignore Armor are multiplicative as well. ensuring that you'll have at least 30% of your Armor (yeah, that's not much, but it happens when you let them build up pure armor pen. Randuin's still beats the **** out of that sort of build still).