Between the two options:
1. Keep Black Cleaver as-is
2. Remove from Dominion

Which would you choose and why? Keep in mind the global penetration aura is being removed.

1

1 personally. Ad casters have almost always tended to struggle as is in dominion (at least in my experience, though I don't main them). This gives them a chance to stay in the game past 5 minutes.

3. Make the passive unique.

Neither option you give is viable. Removing it outright kicks AD in the nads; leaving it in as is allows for abusive item combinations that'll hurt Low ELO/Entry Level Dom more than high level play. It's basically the 'Kassadin Effect' in item form.

what aboutthe ption of removing the aura and leving bc as it is? well if i have to choose an option as a whole i'd choose two, armor being made harder to get by and BC not being unique is still gamebreaking mostly because the item was designed for ad casters but the stats it gives are useful for everyone, even Udyr and missfortune want BC since it tears through armor really really fast making the opponent waste a lot of gold in the case they itemized armor instead of hp (a hard stat to come by in Dominion), It basically Punishes armor stacking: Good thing but it's an overboard punish

ITT: Nome just found out he can't make a Dominion Exclusive version of Black Cleaver.

Just make the pens Unique that solves it as of Now removing it would just postphone the discovery of the item being OP anyway

Also BC as meant should be a situational Item that you buy when you got a hella of Armored Oponents and your teamates are mostly AD(heck it was designed to be SITUATIONAL-Phreak,Morello or Xysoherous said that on the forums- on AD assassins Like Talon and Kha not Stack till fills all inventory Spaces ) of now its Basicaly BT 2.0 where your only option is stack it till no tommorow to both be A-Deal Dmg and B-Tankiness as of now you can't buy Armor or MR without risking to be Instagibbed

Lame :/
Regardless, good on you for recognizing how strong it is and proactively changing it.

If given the option, I'd say remove it until it can be fixed for Dominion. However, I really think that the SR people are eventually going to figure out how strong it is, and that passive will probably become Unique in time. We just need to wait for them to catch up with us

Out of the really crappy options you are giving us I'd choose #2. AD casters were OK without it previously and with the new way Penetration works I'd say they are fine. Black Cleaver is really only helping tanky derps and it's clearly far too abusive on some like Jarvan and Wu Kong.

Also, who's bright idea was it to add HP on to it? That just makes it more viable for tanky dps. If you want an item that is primarily for AD casters, remove any tanky stats from it.

If you really want, bring it back when you remove the Pen aura just to see how things shake up.