I don't understand your argument. What is wrong with his W and R? Are you saying they are strong or weak? Because both are wrong.
Too much power in his W leaves the rest of his kit weak
His 40% AS slow is the primary reason most bruisers can't fight him
Needs to lose the AS slow and get a reset back on R so he can actually get picks
Too much power in his w? I find that his Q is the main reason people don't get close to the minion wave, his W is mostly used as a slow in the early game.
Rest of his kit weak? He has a decently long range hook considering the rest of his abilities, he has a AoE damage ability with no cast time and short cool down, and he has a reset-able execution ult.
Most bruisers can't fight him because his early game is meant to be borderline OP. He can force people into bad fights with his hook, and poke people with the edge of his Q. The W attack speed slow barely makes a difference, which is only 20% at rank 1 btw, because no one should be able to fight him early on.
Sure, the double slow on your carry or something might be very annoying, but if Darius gets in range to W your carry, chances are they are going to die. There are also quite a few other champs that bring double slows to the table, Nasus being a great example, with a longer range scaling slow that pretty much renders anyone useless for 5 (!) seconds.
And he needs to get a reset back on his R? What? It...It already has, and always had, a reset...
As a side note, I had Darius on my mind during all this and decided to play as him and enjoyed winning lane super hard and just dunking everyone later on. So much fun.