Let's give Darius %hp true damage on his ult

Because #1: Darius is not vayne. #2: Vayne is THE DUELIEST DUELIST of the duelists, Darius while extremely strong at duels is not meant to be the duelist that vayne is. #3, because Darius is already a STRONG top-laner, his problem however is the Yorick problem which is why he does not often win games The yorick problem: Strong at laning, but doesn't transition well into a team-fight... since league of solo queue and league of 5v5 often end up in team-fights darius falls off strongly.

Because the amount of true damage that Darius and Cho'Gath do is greater than the percent damage Vayne has on her Silver Bolts.

It's like Poppy's Q is the only % health ability that has a cap on damage to champions, but you need over 4k HP and 0 MR to hit the camp anyway so whatever.

The thing with Darius is, he needs to stack his passive before he ults. If you can do that you don't need fancy things like %hp true damage.

Oh gee

Maybe because they are different champions?