About Cassiopeia...

In my opinion, Cassiopeia is slowly turning into what you did to Evelynn after you severely gutted her a few seasons ago, to the point where you were reported for playing her. She's barely relevant in laning phase where you can only farm and pray you don't get ganked or die, because if you do, you might as well just leave the game and not weigh down your team.

If Cass doesn't get ahead, she's just a stun bot then fodder for the enemy team, especially with the gutting of her passive hampering her powerspikes. Her E is meant to be spammed sure, but you can only cast four or five Twin Fangs until you completely drain yourself of your mana and become an open target for retaliation.

You admitted yourselves that Cass is an extremely bad spot but...it just seems you're ignoring her presence entirely.

I feel like something as small as gaining x amount of passive stacks upon assisting or killing an enemy champion (maybe less stacks if it's an assist). It'd certainly be helpful, and allows her to hopefully gain back some relevance should she fall behind in a game.

Edit:

As I thought about other possible changes, you could make Cass less reliant on E, and instead give more possible combinations.

Here's what I'm thinking: Cass' Q does poison damage over time. However, should she strike a poisoned enemy with her E, they will receive all of the DoT damage in one instance. Her Q's poison also no longer resets her E's cooldown.

Cass' W would allow her to do what she does now, if you're hit by Miasma, Cass can repeatedly cast E as long as you're in the Miasma field.

Of course, there's dozens of other ideas, but I just thought these would also be interesting.