You can't use overall win rates immediately after reworks.

There are so many reasons why after reworks, you would expect win rates to go down across the board. First, you have a ton of people first timing these champions to try out the changes. First timing things = lower win rate, they aren't as experienced with the champion and will be more likely to lose due to that inexperience.

Secondly the old mains now need to figure out what is optimal for the champion and that is a trial and error process. In terms of both new mechanics and builds. Combine that with item changes and you get mains losing more than before, due to attempting to figure out what exactly to do.

The win rates probably won't settle until next patch when all the bandwagon players stop trying the tank changes and mains figure out what s best for their champion. Then if champions like Zac are still doing poorly, I am totally on board with another wave of tweaks. But for now people need to chill, the win rate is not going to reflect the true strength of a champion until people stop first timing the changes in ranked and learn what to build again.

The only thing you can REALLY know for sure is that if first timers are crushing on something reworked and their win rate spikes, the rework had some stupid numbers on it .