so im running numbers right now, and im using Rammus as a model....no runes, just masteries
with Rammus' W active, and having built Thornmail, the armor boots, randuin's omen, sunfire cape, frozen heart, and GA, he has 530.25 armor.
if the opponent has just 1 BC built, and no other armor pen, the armor for each successful hit that gets ignored is
1st 62.42 (0 BC stacks)
2nd 102.19 (1 BC stack)
3rd 141.96 (2 BC stacks)
4th 181.73 (3 BC stacks)
5th 221.50 (4 BC stacks)
now, add another 15 onto each of those numbers for each BC they build after the first. if they build 4 cleavers, thats over half of his armor ignored after the first attack only, PLUS thats 200 AD and 1k HP to boot. the passive and the ArP on it should be unique just so theres not so much armor being ignored after 1 hit