Arguably the biggest issues with Armor Penetration, and a quick fix

When it comes to lethality, people argue that it offers too much damage and ruins tanks. However, it's not lethality alone which does that, it takes a build of 5 penetration items .

And this makes sense: if you stack literally every form of armor penetration, you should be able to ignore armor effectively. The issue that stands is twofold.

1. The % shred items offer too much flat AD in addition to the penetration. This keeps the items decent against squishier targets, which these items are not meant for. This is seem most used with Black Cleaver. The item will be picked up quite often 1st or 2nd by bruisers, as well as later on in builds by casters and assassins, while remaining effective against all targets (who at the point of the game it is picked up, shouldn't have enough armor to justify the shred being over effective). Now changes went through just this patch looking at this, lowering the AD on Black Cleaver and raising the health. But I'm not sure that adjustment wasn't large enough to make it less desirable on casters and assassins. I'd argue another 5-10 AD should be removed from Black Cleaver, but instead of there being a health increase to compensate what should be adjusted is the number of stacks to max out the shred, moving from 6 stacks needed to 5.

2. Currently, each Lethality item gives 20 out of combat movement speed. This isn't too much early on, but once all lethality items are stacked a champion can get up to 60 flat movement speed out of combat. Essentially this gives champions stacking the items the ability to have levels of out of combat movement speed while keeping an optimal level of in combat movement speed. The in combat movement speed is even greater when considering and its spammable active. As for a fix to this issue, the out of combat movement speed passive of the items should be made unique, while increasing the amount on an item from 20 to 30. This way, the out of combat movement speed is maximized at one finished item while not being overbearing when stacked.