@Stashu: What Cassiopeia should be vs. how your Cassiopeia turned out. Complete with videos!
Skip to the 0:35 mark. This is what you turned Cassiopeia into.
https://www.youtube.com/watch?v=-_ZeD40Rg8A
To explain in more detail.
If you look at Cassiopeia, her personality and appearance fits a spoilt noble-woman who prefers to lounge around and rely on debilitating magic to wither her foes before going in for the kill. Hell, maybe not even going in for the kill, but watch them die as they slowly stumble towards her.
If you look at Poison-type archetypes, unless they're assassins with a dagger, most of the time their MO is to stand back from a vantage point and flood the battlefield with deadly poison or poisonous animals.
THREE THINGS are core to this identity:
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Both identities are not duelists. They do not wish to face off an opponent like a samurai. They do not wish to go mano-a-mano with her opponent like Xin Zhao.
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They want to just poison from a safe distance and then GTFO until the poison wears off.
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Their weakness is being engaged upon before their poison can take into effect.
(oh, and poison should be satisfying, without launching gigantic fangs larger than your torso)
This is where your rework that puts 99% of her focus onto her E fails. She's no longer the elegant manipulative poisoner that she should be. She's a mano-a-mano AP brawler.
You turned Cassiopeia into "Magical Kenshiro"
Such a concept can be cool on
or
. But not on 
TL;DR - Less Magical Kenshiro and more the snipers from Blighttown in Dark Souls
edit: Shit...I put videos as plural in my title. Erm...here's the part where Korra was poisoned in Season 3 of Legend of Korra.