Buff Darius
He's immobile with no escapes which is basically a death sentence in todays game seeing as everybody and their mother has a form of dash/hop/massive speedboost or all lumped together.
He's either a slug fest with another melee to death or he's a I cant reach you so kite me to death ranged champions, his pull isn't enough as it has a wind-up time and has 540 range from 550.
His whole kit revolves around his ult which got nerfed to no longer fully reset so he can no longer keep late game champs down as well.
His movespeed bonus, it isn't amazing guys, 5% for each bleeding champ, chasing a champ at level 1 with no items and them bleeding makes you barely able to keep up with them and even then just barely.
He has no innate tankiness or sustain, every other bruiser/tank has one of some sort, he's not tanky without risking his whole build being built into tank items except maybe 1 damage item.
Oh he has an ability which lets him get penta kills in games? He can't have something unique in this game but I do see your point, he's similar to Garen in terms of ult as they both get the most out of it ulting low health enemies, garens is better on health stacking enemies and Darius is better on people within health range of him getting his reset.
His scalings need to be adjusted to fit his play style if he does get reworked, if he's going to beneft from building tanky only(maybe 1 damage item) his scalings should be total AD not bonus AD.