@Stashu: Possible Cass solution to make nearly everyone happy.
Edit: See, Stashu? People don't even like it when it's as close to old Cass as possible. The people have spoken, revert the rework.
So, while replying to someone in Ginga's last Cass thread, I had a bit of an idea. It was so simple and could be so effective at both making Cass fun and keeping the rework direction (and even keeping the passive, in a form) that I had to draw some attention to it.
It's simple, really. Add Deadly Cadence back...as rank 2 of her passive.
"But Deadly Cadence is what made her a bully!" Yes, it did, but now it'll be gated behind her stacks. "But gating is what you guys don't like!" This is true, however we primarily don't like it because it feels bad: the benefits are largely hidden, there's no additional gameplay in them and they feel like they were stripped from her base kit. Cadence isn't hidden, feels great and adds gameplay--oh, and it helps with her mid-game mana issues, too!
"But Deadly Cadence isn't thematic!" On it's own, no it's not. It "sort-of" fits in with the rhythm of a snake's movement, but it's a bit of a stretch. However, it does fit in with the "gaining power" theme you want to take her in. "How so?" Glad you asked. If she's learning to embrace her curse, then she'll want to use it as much as possible. Simple as that. Snake lady like to poison things. Snake lady poison things lots.
"But she'd still be a bully!" Well, not really. Since it's gated by stacks, she'll only get Cadence by the time the laning phase is ending or already over. No laning=no bully. Meanwhile, she needs mana to teamfight and kill baron/dragon/blue buff, but E doesn't give it to her if she doesn't kill creeps with it. With Cadence she gets to keep that blue bar filled without needing blue (so your jungler can have it) or a Seraphs/RoA (which are otherwise must-haves).
Apart from that change, the AP bonuses and cooldown reduction need to go. Put the CDR back into her kit so she can use Q without it feeling so awkward. W maybe doesn't need it, R doesn't either (though to compensate, a slight reduction would be nice).
As for the AP bonuses, we've still got a third rank to work with. Instead of just dumping the 30% AP into her at rank 3, why not make it a part of Deadly Cadence? X% more damage per stack, maybe? That'd feel a whole lot better than just a flat bonus, even if it is strictly weaker. Gameplay is better than stats.
The first stack can stay as-is (the 5% AP bonus is pretty meaningless at that stage, so it's no real loss). The sustain is welcome and does add gameplay.
So, Stashu. Does that meet with your approval? Cass players, this seem like it'd feel good?