You made Darius a better character now make him a better champion
Riots afraid to change concept always sticking with bad attributes that not effective or interesting (such as being super vulnerable against poke/kite, having 0 utility/engage). Well they left him with stacks and true damage nuke (reset) and these things is actually what make Darius who he is. Stacks, nuke, reset. This is the idea. Ruthlessly destroying everyone on his way 1 by 1 splashing blood around. Ye sure thing Darius needs to achieve this scenario by tryhard. Here comes the problem. He pulls his team down by his gameplay. He does literally nothing for teammates when he have no opportunity for dunk mode. Slowly walking around untill someone engage or simply eating poke. Stable wave clear? Hell he deals 0 dmg to super minions and structures. When you have Darius on your team opponents always abuse this by fast rotations, turtling, hit and run strategy. You literally will be playing 4v5 unless d-man finally catch someone (reminder that he deals not that reliable amount of late game damage). This is why no one use him in lcs or at least in solo q high elo. He has solid counterplay options but suddenly no answer to this at all.
Heres my opinion how to increase his strategic value (ye this is what he lacks most, not even mobility and stuff). 1 The easiest way. Make his damage against objective untis (nashor, drake, turrets, inhibitors, superminions) comparable with carries. This WILL force opponents to finally attempt something. No idea about the formula. This might be Noxian Might activation against objectives or % increased dmg on W (Solid reason for him to learn W instead of blind 2nd maxing armpen from E skill.) This thing shouldn't be possible pre 20 minutes. 2. Worse one but still reasonable. Sacrifice offensive side by doing 2nd version of pull that applies solid (not less than 2 seconds) CC instead simply slow. Good option to engage or defense. Champions that got affected by spell will get bleed-immune status for 5 seconds. You may perform this only when you activate W and smash E with empowered attack up. This will also waste empowered attack and send W on cooldown. 3. Say no to dunks. When Darius ults someone without any stacks this will grant !massive! movement speed buff to allies around (850 range). Buuut no dunks, man. Still better than being kited without any hope on happy ending.