Seems odd they went with making Cleaver into a second % pen item, especially with Last whisper as such a strong % pen option already. I think the %/flat mechanics change was needed, but a second stacking % pen item wasn't...

I think they should just readjust the stacks honestly. Add an extra stack or 2, make it something like 4.5% per stack and have it stack 6 times, or have it do 13% per stack and only stack twice, so it's a waste to stack them. The problem I see with these solutions is more for the first that it takes to long for a caster to stack, and with the second that ad carries can easily stack it then.

So I would propose that black cleaver only stacks on physical spell damage, and does not work with basic attacks. 2 stacks applying only from spells allows talon to rake and stack it for example. If it's for casters, make it apply based off of casting spells, wouldn't that be common sense?

I would even go as far as to say increase the flat pen and lower the percent pen, this buffs the early game and weakens it a little bit late game against tanks. Maybe they could replace the ruby crystal with a vamp scepter and raise the price some, giving ad casters a way to sustain some as well. There's so many ways to alter the cleaver, should have gone through more extensive testing.

I still feel that this should be an AD caster item, not a replacement for Last Whisper. You are supposed to pick up the LW to counter tanks, so what to do with BC?
Probably needs to be increased in AD and remove the armor shred. The armor shred is what is causing the problem. Leave the armor pen and cdr stackable.

This is what I was hoping they'd do. It's still the great item that AD casters and bruisers want but it's no longer the only item someone needs. I really don't understand how Brutalizer needs to be nerfed because the item it builds into is too strong.

It's an AD caster item whether or not it's stackable. Generally speaking there's been a long standing trend of stackable items being changed to make stacking them unattractive.

Even if she was doing true damage, which she definitely wouldn't have been, she still couldn't possibly 4 shot you. How does Riven, with only 210-230 total damage 4 shot someone with almost 4000hp?

I don't know. I don't play Riven. Maybe I miscounted and it was 5 hits? Doesn't her Ult do percent damage? Either way, I had way more build than her, obviously more gold, and she was able to negate all of it to the point that I was no longer able to reasonably act as a tank. Not even sort of.

I'm not saying armor pen shouldn't be a thing...but you shouldn't be able to just burst well-built tanks down in a couple seconds using only 1 character. Otherwise...what is the point of playing a tank?

Let me phrase this another way:
It was before you had:
1 shred item (malady/black cleaver)
1 pen item (sorc boots/brutalizer)
1 %pen item (void staff/last whisper)

Additionally, you had abyssal, which I suppose was available because of huge mres items like FoN and AP casters 'usually' being more bursty.

Riot says that tanks are outclassing these items, though, so they:
reverse how % and flat pen stack
nerf tank items
buff several AD/AP bursty items

But then, they ALSO changed the AD shred item to BOTH shred and % reduce, and made the shred easier to stack AND make it non-unique, AND added base pen to it...

If you kept all the changes EXCEPT the BC buffs, I feel like it would have addressed the issues fine...but WITH these changes, it's WAY WAY too much. With Masteries, BC and Last Whisper you can now stack almost 75% armor pen...that's CRAZY.

Her ult gains bonus damage depending on your missing health, potentially doing double it's minimum value.

The Riven you described would be doing, with her ult's damage buff up, ~345 damage per AA proc'ing her passive, a 300 damage W, 670 damage if she hits with all three of her Q's, and a maximum damage of 720 with her ult. Not inconsiderable, but it still requires her to connect with all of her abilities and then AA 7+ times, and that's ignoring whatever remaining armor you might have after the reduction and the fact that she's not going to proc her passive on every AA.

She's still doing a lot of damage, but it's not nearly as scary as suggested.

Except for the fact that LW+TBC+same runes+masteries from S2 would leave the same target with 67 armor, and you'd have more AD and more AS and it costs 135 gold less.

The problem isn't the numbers (IMO), it's the fact that it stacks.

Ok, pulling up LOL replay (forgot I had this), watching an earlier battle with me at 2663 max hp and 77 armor, before I started building armor and after she got BC and LW (I know, oversight on my part), she was hitting me for ~400 damage on her normal abilities and her ult got the last shot for somewhere around 5-600. So, it took her about 4 swings, +1-2 attacks from her teammates.

Also, checking her stats, she had 40% armor pen between LW and Masteries, as well as 20 flat from BC/Masteries/Runes at this point. Meaning at this point she was doing true damage...not surprising given I hadn't built armor yet. My fault...so I say "wow, I'm dumb, I'll build armor!"

Fastforward

I get a chain vest, putting me up over 120 armor, but Riven still hits for over 200 (close to 300) a swing, with the addition of only phage (20 AD, not a big change), and being 2 levels lower than me. Her ult still wrecks for around 500 damage... her combined pen still has her at close to true damage before her ult hits (only 34 of my armor counts).

Ok, I need more armor...right? I'll finish a sunfire cape and grab warden's mail! Super armor HO!

194 Armor now, but Riven's gotten a bit more AD (bilgewater, and finished Frozen mallet)...and now she's hitting for 4-500 a hit? wow! I spent over 3k gold on tank items and she added a little more AD than you'd get from a BF sword (lets say 2k gold worth) and is doing significantly more damage, still...

What is my armor even counting for right now? 194-30% from BC = 136 -40% = 81 -20 = 61

So, for the low low price of around 3k gp, I got less than 30 effective armor...her ult alone is hitting for 5-600 damage even with no BC stacks on me.

Ok, so what if I just went balls to the wall with the Armor? Just stacked Chain vests? I had I think 3 slots left when I started building armor, 3 chainvests would be around 2.1k, for 120 armor (25 more than sunfire/wardens), leaving around 900gp to make 2 of those warden's mails instead of chainvests...ok, that would have put me at 243 armor...or as Riven likes to call it 82. Turning a 140 armor increase into a 48 armor increase...

I guess next time just build HP since they're gonna ignore whatever armor you buy anyway??

TL;DR? There is no way to build effective resists against the amount of penetration available now. Even 1 BC is too many.

All they needed to do was nerf the maximum armor shred (because it really was too much) and make everything unique. I have no idea why they thought allowing them to stack entirely, when they provide health and damage, was even remotely a good idea...