My thoughts on Cassiopeia's balance
I'm not claiming to be good at champion balance and numbers, or that I am a god Cassiopeia main. I've been enjoying playing Cassiopeia ever since 2013 and I just thought I'd share my opinions on her recent rework. I have tested her rework on the pbe before her launch so I'm fairly experienced with her new kit.
Passive: This is one of my main problems with the kit. It's supposed to be a bonus right? Wrong. Serpentine Graces not only forces Cass to miss out on boot stats, but it also forces her to have a very slow early game. For a champion that's supposed to be swift, her passive isn't really an actual passive till lvl 14 when it actually gives her the same movement speed she would have gotten at about lvl 8 with boots. And before you mention the glorious free item slot she now has, remember that most games don't even last long enough for her to benefit from it, and having Cassiopeia wait till uber late game to have a meaningful passive was actually one of the complaints from the older rework. My suggestion: Buff her base movement speed by alot and have it scale less.
Q: Overall happy with how it changed.
W: I have mixed opinions about this spell. While i like it's catching capabilities, it's damage, and it's casting paradigm, the fixed cast range is a whole new level of annoying. You can almost never use Miasma to stop someone from chasing you as a mere silence and a rapidly decaying slow doesn't really stop people from just jumping on you and when they do, you're fucked. Fixed cast range mixed with an unreliable way to get an MS boost and a pitifully unreliable ult means that Cass is just meat for anyone to jump on. My suggestion: Remove the fixed cast range and the wall interaction. Have the number of circles decrease in direct proportion with the range so that it's like one circle when Cass decides to cast it on top of herself OR make the slow not decay so it becomes useful disengage tool.
E: Again, for a champion that's supposed to be swift she sure does take alot of unnecessary pauses to use a "spammy" low damage (that includes having the target poisoned beforehand) spell. With this rework you had the opportunity to make her feel actually swift by removing the cast time but now the cast time is still there, it does low damage, AND it's not as spammy as it used to be. The 1 second CD adds to Cassiopeia feeling slow just so it can be a farming tool. My suggestion: Reduce and cap the CD to 0.5 OR remove the cast time OR increase the damage significantly when the target is poisoned, the risk is simply not worth the reward.
R: It's issues hasn't been fixed and it has been instead nerfed for no reason what so ever. The stun is pitifully unreliable unless she's hiding in an unwarded brush. My suggestion: Increase the slow even more than 60% so it can be a more reliable disengage tool OR remove the delay.