I personally liked the old mechanics/kit (either of previous iterations) better. The league community didn't like her Twin Fang (or was it just the focus on it from the last kit?), which I thought was silly, since she pretty much plays like an ADC and you are pretty much doing the exact same thing with the same finger on the opposite hand. From the changes, her damage focus did shift toward poisons, away from Twin Fang. I think the old MIasma mechanics (growling cloud/circle of poison with persistent poison) still suits her kit better (being able to have more poison to combo with Twin Fangs and also lower CD, also granted vision in bushes). It 's sad to me that players are too lazy to learn her difficult playstyle, but no one complains about other high skill champs (Draven, Lee, Azir, etc). Riot could have just shifted the base/ap ratio damage towards Q and W away from E in her old kit- I don't know why the mechanics had to be changed.
However, she played a lot better today after the patch 6.10.
Maybe someday we'll get the old Cass back. :/