Okay, so first off the news that % and flat armor penetration will begin stacking in a more beneficial way is something that I think is really awesome and I find to be quite exciting, however it seems like that will leave armor shredding abilities/items in a very bad spot.
Take for example a 60 Armor target. You have Last Whisper, Van Damn's Pillager, and are Olaf at level 18. This grants you 40% armor penetration as well as a flat 55 penetration. This means something needs around 90 armor to not be taking true damage from everything you do.
If you were build a Black Cleaver (Yes I get that I am proposing a pretty silly item build just for the sake of my query.) to help shred the armor of some of the tankier targets, will the shred on-hit be completely lost on targets that have enough armor to not be reduced below 0 armor but also low enough armor that your champs armor penetration bypasses all of their armor without it?