riot has not only nerfed the items base AD and % armor pen stacking they also changed the build path to the item which since then makes it alot less friendly and attractive for an adc to get this item.
a few still might but the item it self dont automatically give them armor pen unlike last whisper items... they have to attack you and do it over and over to stack the % armor reduction
so 40 ad and 4% armor reduction per stack up to 6 stacks (24% total) isnt that strong of stats for an adc... yes its easier for them to get the stacks but let a crit base adc with out black cleaver auto you 6 times in a row and see how powerful crit is...
also the item isnt practical for single target based crit adcs in the 1st place... its is best on champs that have on hit effects like lucians passive or mf's double shot or their ults... which both are caster type of adcs who need the cooldown reduction and consider to be more "short ranged adcs" so the hp stats over them some security
the major issue with black cleaver on adcs isnt the damage... its the movement passive of phage in the build ( which is great for melees cuz they need the help ) but the security of being able to have more movement speed based on damage is where i think it effects the "balance " of the item for range marksmen
so maybe as an alternative just make it where if you are consider ranged the movement speed passive dont work... but you can still get the item
