@Riot PLEASE read this! Revert Cassi, there's an easy tweak that would keep her gameplay healthy.
The small tweaks I'm suggesting are:
- Revert Cassiopeia's rework
- Increase the cooldown of refreshed twin fangs from .5 seconds to 1 second.
And that's it. And she would be perfectly balanced. And this would take a single patch to do. Cassiopeia's rework was just a large heap of numbers, and I'm not saying that in a quality sense. (Although this applys in that sense too) I mean that literally the only thing Riot did was tweak her numbers. Cassiopeia's prework and post-rework abilities are identical in function, aside from her new passive.
Cassiopeia's old passive was called Deadly Cadence. Casting a spell would cause any subsequent spellcasts within 5 seconds to cost 10% less mana, stacking up to 5 times, and rings would circle around her as she stacked up the bonus. When Cassiopeia gains bonuses on her current passive, Aspect of the Serpent, snakes start circling around her. Riot could just use these snakes as the visual indicators for Cassi's old passive if they reverted her.
But, to those who don't know, a revert to Cassiopeia would look like this.
Current Cassiopeia: Q: 75/115/155/195/235 + 45% AP W: 10/15/20/25/30 + 10% AP Mana Cost: 40/50/60/70/80 mana E: 55/80/105/130/155 + 55% AP Mana Cost: 50/60/70/80/90 R: 150/250/350 + 50% AP
Old/Reverted Cassiopeia:
Q: 75/115/155/195/235 + 80% AP W: 25/35/45/55/65 + 15% AP Mana Cost: 80/90/100/110/120 E: 50/85/120/155/190 + 55% AP Mana Cost: 30/45/60/75/90 R: 200/325/400 + 60%
...And, aside from that, there are barely other mana cost/ cooldown changes, if there are at all, and those would be very negligible.
So, as you can see, the old Cassiopeia is significantly stronger than the current one, but considering how badly the current Cassiopeia is performing, I think that'd be okay.
A VERY IMPORTANT NOTE is that old Cassiopeia's E had a .5 second cooldown refresh as well, but it was on hit, not on cast like live. So, the cooldown wouldn't be refreshed until Twin Fang connected, instead of on command like now. I'm suggesting a 1.0 second cooldown refresh, ON CAST. This would make her E spam at about the same level as old Cassiopeia, which really was only at about half the speed of current Cassiopeia. Cassiopeia's main issue right now is that her laning is oppressive due to her twin fang spam, but hitting that, it gives her opponents more room to breathe, and more room to to buff the rest of Cassiopeia's kit, which was trashed in the rework.
What do you have to lose by giving this a chance, Riot? It's just number tweaks, so it wouldn't be very time consuming. And Cassiopeia has been performing very poorly as of preseason. She needs some buffs, and not saying my suggestion is perfect, but it's definitely worth a shot. You just need to give it a chance.
And I'm sorry, but saying Cassiopeia was problematic before is utter bullshit. The only changes you made to her pre-rework were BUFFS, so how was she problematic in season 3? And Season 4, where, after the 2 small buffs in season 3, Cassiopeia was not changed at ALL?
As a final note, I'd just like to say, if any Rioter has read this post, please comment on it. It would really be helpful to have some communication on this.

Yeah because forcing a mage to be an adc worked so well last rework.