i don't think darius needs direct nerfs
at least, the passive nerf isn't. he was overbearing because of CoC and the top lane meta the last few patches
the top meta briefly switched to almost entirely tanks thanks to how CoC worked. Darius's biggest counters
have been phased out, and Darius himself is a strong counter to most if not all tanks, especially Poppy who is also getting nerfs, as well as Yasuo, who's very popular top lane
CoC also made Darius much better at trading with champs that counter or go even with him
etc. the shield made his losing matchups way more forgiving as well as turning even matchups into his favor (most of these champs can't or don't want to use CoC, giving him a one-sided advantage)
also that champs that used to beat him in lane
have been neutered and lose to him solely because they're just bad right now.
CoC is the biggest reason for his winrate going up; it's already been slowly dropping off, and further nerfs to the keystone will see his winrate stabilize back to 50% as it's been for roughly a year.
i don't think Darius should be nerfed in the same patch that we nerf CoC; in my opinion, he is balanced very well right now, it's the keystone that pushed him over the top.