Alright, let's try this again.

Hypothetically, if... (ALL OF THE FOLLOWING HAPPENED)
1. Brutalizer's flat armor penetration did not stack with Black Cleaver or Ghostblade...
2. Black Cleaver's percent armor penetration were slightly nerfed...
3. And Brutalizer and BC's flat armor penetration are nerfed from 15 to 10...

Would it be OK to keep Black Cleaver on Dominion? Opinions, now!

Is Ghostblade still 20? Is Ghostblade still stackable with Black Cleaver?

I agree with 1 and 2, but why the flat pen nerf on top of it? That's just overkill. It's basically railroading stacking all of them or you are worse off than you were pre-season with the same items (youmu/lastwhisper).

I would say yes, it would still make BC a to get item, with HP+AD, but I least armor won't be 100% useless anymore.

Yes it would be OK to keep it, I already feel like BC+LW+other items is better than BC+BC+LW, but it of course it is all about countering the Frozen Heart / Thornmail spam.

Personally I'd like to see the Health on the item disappear or become unique, so that we can still build super duper antitank if we want to but we'll be really squishy for doing it. I suppose that's LW's job, but LW doesn't counter FH or other armor stacking as well as one would hope.

The reduction of the flat pen though, if it no longer stacks, doesn't make sense.

I'd personally like to see BC become unique, but us still be able to stack flat pen using different items, and possibly the health gone from BC.

Why Brutalizer not stacking with Black Cleaver or Ghostblade over Black Cleavers/Ghostblades not being stackable? Using Brutalizer and stacking it with a finished item is an item slot you're trading off for the increased arpen. I'm okay with Brutalizer stacking with its upgrades, but I'm not okay with the same upgrade stacking with itself.

If Black Cleaver's % reduction is slightly nerfed that should be fine, but then again if you're removing the global pen aura I'm not sure it's completely necessary.

I think the flat pen values are fine by themselves so long as they don't stack (for the same item).

Yes, it should be fine, assuming the pen aura is getting removed as well. Depending on how the numbers on #2 work out, Cleaver + LW + armor shred hero shouldn't automatically mean everything takes true damage.

By 'slight' nerf, I'm assuming the 30% shred is dropping to anywhere from 20-28%?

There's still Darius.

I really think the only problem is that Black Cleaver can stack. It needs to have unique passive and unique armor pen. There's no reason to nerf other items when the problem can be fixed just by making the passive and armor pen unique.