Yet again, the Cassiopeia reworks are a rousing failure
Passive This is the only part that doesn't seem to be complete trash, since it fits in to the fact that Cassiopeia from a flavor perspective has no feet, and from a gameplay perspective in that she wants to be fast and manipulate movement. I'd give it an A for effort, an F for execution, because it really just seems to have been used as an excuse to make her slow as hell. It scales poorly and her base speed is so low you may as well be glued to the floor. It's also a failure in the fact that it's just extremely boring. 4 speed per level? That's all? You can't think of any other way a serpent is graceful? (Hint: it's how they strike - give her some rewarding clauses for being aggressive and landing shit -duh!)
Q The range nerf makes the movement speed buff on this useless, as you're in range of pretty much every ability of every champion ever. You won't be using it to advance unless you're already on them and you won't be using it to get away because they're already on you. Garbo.
W This is terrible. The Grounded effect is a cute idea, but the usage in this skill makes it pretty much useless outside of a team fight where you aren't being focused. It's always max range and it's not horribly thick, avoiding it is easy for a lane opponent due to the fact you have little control over where it lands. Is that why you made it so stupidly huge? To mitigate the fact that it's so unwieldy it may as well do nothing? Not to mention that this was the easier poison application. If you change E for why I think you changed E, then changing W this way undoes all of that progress and makes her LESS new player friendly.
E Literally the worst change of all. Primarily because it completely butchers the identity that Cassiopeia has had since her release - one that she shared with Anivia. Apply your debuff, then unload. Anivia did that with extra damage because she was "slow and bursty". As the "fast and DPSy" alternative, Cassiopeia did that with machine gun fangs. Now, Cassi is a muddled mess of slow and DPSy. The extra damage and heal being applied to the poison condition isn't very helpful and really just makes this way weaker for farming (which is a use case I didn't like being added with the last trash rework but here we are) and sustaining in lane. Especially with the huge hit mages took to mana regeneration itemization (which is fine it seems) it causes a situation where not only does Cassi spend more mana to earn back mana from E - it's not worth it.
R The cooldown reduction is just undoing some of the extensions the first rework's stupid passive caused her to get. Totally understandable. The slow reduction? Punishes opponents less for reacting accordingly to her ultimate if they can't get out in time. A+ change. Hell, S+ change if I'm being generous.
So in conclusion, why??
Why change all her basic skills in ways that just make her less rewarding to play?
It seems like you had a good idea with this new passive, but then decided "well, that's finished" and romped your way through everything else half-assed. The passive and R changes are fine, but the passive really needs to be a lot more interesting. And for Cass's sake - please undo or at least revert large parts of Q, W and E.
Funny enough, the last time I took to the boards was to complain about yet another awful rework to Cassiopeia. Has anyone actually working on her ever played her? Do any of them actually care about her as a character? Each change just strips away parts of the identity she was conceived with and the identity that she built both from a gameplay perspective and from a lore perspective. What's the point of making a character with a nice design if you're just going to dump all over it every few years?
