Darius should have power moved away from dunk burst
this is the best way to balance him across elos because in higher play he simply doesn't survive long enough to make use of his power and in lower levels he is hard to deal with on account of his sudden and heavy burst potential.
Reduce his ult scaling, maybe nerf Noxian Might's AD as well, and then raise his attack speed per level so that into the mid and late game Darius can more reliably make an impact in the game without basically needing to be spoon fed a reset by his team before he's threatening.