Seriously. Darius passive triggers the 30% cleaver armor shred proc over the course of its duration. That's kinda insane, especially since it's armor and not bonus armor.
Armor pen doesn't stack like that. BC pens 30%, then his passive pens % of the rest of your armor. I have problem with him that he only needs one AA on you in order to stack up BC to maximum. Maybe doesn't seem like a big thing, but one Q in teamfight easily makes you frontline 30% squisher for his ADCs. Also armor pen doesn't metter that much. He will stack his passive on frontline then flash+Q on backline and then DUNK DUNK DUNK DUNK. Maybe it's worth something in lane, but...
