You stumbled upon the true problem with most bruisers. They are specifically built in a certain way that makes any changes have unpredictable and harmful effects. If i look at the upcoming patch and apply logic to analyze.
Black Cleaver OP->See which champs benefited most from it->look at personal opinions->look at community opinions->nerf select champions.
However in some cases i think its a bit over the top such as in Riven's case
Black Cleaver OP->Her win rate went to 54%(currently 52.78)->xeph lost to her top lane badly and thinks she needs big tweek->some people think shes too strong early game->applied changes to make it so trading doesnt work as effectively and hurt her lvl 3-11 game. However from so far in the poles it looks like they applied personal opinions and didn't look into community opinions as much.
If what we see from the poll is true then Darius has strong top game, hes standing at 52% win rate, community thinks he needs balance, riot doesnt.