I think that the nerfs on his passive damage were mostly uncalled for. I don't really care about the handle, if you're not an idiot, you should be able to hit about 75-80% of your q's. The problem with darius is that the way to counter him is not engaging in longer trades or fights with him, and that is something that most people in lower elos are uncapable of. Also people tend to get hit by the outer circle of the q all the time, and if they do, they take more damage, get a hemorrhage stack, and heal darius at the same time. That's why he's such a monster in silver/gold, and that's why his banrate is significantly higher in those elos too.
I think the solution to this problem is reworking the w into something that is more than just a +1 hemorrhage stack ability, and giving back the +5% movespeed for every bleeding enemy. With these, he wouldn't be able to win every trade so easily just by slapping another stack on you and slowing you with his w, but he would still be able to completely destroy people in teamfights with his bonus mobility. (if you can land your q's on multiple people or you switch targets)
This could also give a choice to darius players. (do you want multiple people to bleed and dance through teamfights mashing your q and bleeding them out or do you want to get 5 stacks on someone and then take the enemy out one by one?)