[{quoted}](name=Very Scary Dario,realm=NA,application-id=3ErqAdtq,discussion-id=TUet7aBo,comment-id=0000000000040000000000000000,timestamp=2017-07-19T20:57:11.455+0000)
His ult with no items, 5 stacks, at level 18, is 900 damage. A black cleaver makes that 960 damage. That's a 7% increase
His passive, with no items, at 5 stacks, at level 18, is about 430 damage. A black cleaver makes that 480 damage. That's about a 10% increase.
This means purchases of bonus AD increase his passive damage by about 40% more than they increase his ult damage (10/7 ~= 1.4). The bonus AD does a lot more work through his passive than through his ult. Considering the passive is always happening while the ult is just an execute, the raw damage output of his passive is a lot higher most games.
But the raw damage of his passive isn't higher in particular fights, especially towards later game where the bleed, although nice, takes a back seat to the bonus AD gain which seriously empowers Q and R with their insane AD scaling.
His passive might account for a huge chunk of his overall damage throughout the game because it's a beast early and mid game, but towards late game it's all about how much damage his Q + ult can do to hopefully execute the ADC before said ADC fucks everyone over, hence the classic "5 stack the tank then Q R the backline" that darius wants to do in later game teamfights.