First of all, is it just me who thinks that the Black Cleaver mechanic (armor reduction stacks) actually works better with ad bruisers than ad casters or ad assassins? For example, talon or khazix, would not benefit from the max stacks of BC because they do burst damage. A full burst would typically take 2 to 4 hits of physical damage, and as burst assassins they cannot deal further significant damage to utilize the max armor reduction.

What happened was, in my opinion, the ad caster would have wasted all his burst damage just to get the stacks. In a kind of way, this is like a support mechanic for ad casters. The ad caster will do his burst to an enemy to charge the stacks and then his team can then follow up. This is definitely a good idea, HOWEVER, this is not how assassins are supposed to be played. Ad casters (similarly ad assassins) items should rather give more ad and maybe a mechanic that enhances their BURST damage, not a stacking mechanic that does not help in doing burst.

Now my 2nd question is this: Based on my reasons above, why did you have to nerf the ad casters (talon & khazix), when they are in the class that LEAST benefits from BC? Wouldn't it make more sense if you just nerf the other ad champs that have MORE SYNERGY with the item? Yes, I'm talking about ad BRUISERS. what else could be better than an item that has HP, decent ad, armor pen and a stacking armor reduction which bruisers CAN very much utilize because of their longer PRESENCE in a team fight.

Please, I would like to hear your answer, because it just doesn't make sense to me. I would be pleased if you could point out something that I'm missing and explain it clearly.

AD casters get more from the cooldowns and the flat pierce. They have always used brutalizer but then you got a new BC that builds out of an old favorite item and gives extra HP. The extra % based reduction is just that, extra. Talon and zix can use this to kill tanky champs and bruisers, something they normally shouldnt be able to do. It also gets rid of just enough armor to make that final hit particularly devistating. To be honest it's just great for them because AD casters don't have much great itemization specifically for them.

Bruisers can use BC to its fullest but not in the same way as AD casters who use it to just dominate trades. Champs like talon can hit you with that physical damage bleed and shred that armor than finish you off with a followup combo and stuff. But a bruiser will last a bit longer in teamfights and will use the BC as probably intended. They fight back tanks, shredding armor for the ADC and fight their way to other champs dealing all sorts of physical damage and shredding armor left and right. They benefit more from the actual defining passive on the item.

Bruisers have already been taking hits from nerfs to other items. But AD casters? Why punish them all when its just a few going beyond the bounds of their role, also consider how little itemization they have. The first experimental item released on Twisted Treeline was completely removed. An AD item with spellvamp. Or at least I think it was. Never made it to summoners rift.