Cassiopeia, the forgotten one?
Since Stashu's last thread has disappeared a good week ago, I'll have to bring up my most recent concerns in a different manner - in a new thread, that is.
I'd like to discuss the current progress on her rework, or to be precise its apparent lack thereof. You and Morello promised us an update on the PBE in the course of a week - exactly 7 days have passed since then and still no trace of Cass changes. The recent wave of updates only adds to further frustration and overall disappointment, to say the least. Another thing which I must point out is the total neglection she has recieved during those last 3 patches (counting 4.20 aswell), she's still stuck with horrendous manacosts (mostly her E) - the least you could do is lower them, even if it'd be a temporary solution.
Here's some feedback in case you haven't listened before: you NEED to get rid of that passive. In its current state it only rewards snowballing due to its heavy dependence on itemization. Since her lanephase is anything but decent, you'll have a hard time getting the necessary gold to even purchase those much needed items. Giving her some free stacks every few seconds, like you're intending to do, doesn't address that problem at all.
Should you still insist to keep this awful passive, you need to change the rewards to flat ap-gains (+50/+100/+250 on each milestone, they wouldn't stack however). That'd be the only way to ensure that she actually gets stronger once she has finished gathering stacks, no matter how bad her build may look like. And even if you're doing well with the current one, the most you'll get from this passive are 100 additional AP the moment you reach the stackcap. Veigar already gets that much from laning, and you expect her to turn into a hypercarry all of a sudden from this pitiful reward alone? That's just not good enough.
Her kit was initially created to fullfill the role of a poison-mage, one with an actually strong lanephase (if played skillfully) to compensate for later shortcomings due to lack of mobility and short range which automatically puts her at an disadvantage against groups of enemies. Infact most of her damage came from landing her poison, her E only served as a tool to finish off weakened opponents. And yet you try to push her into a direction which constantly forces her to remain in a situation where all of her handicaps become as apparent as ever, all thanks to that sole focus on her Twin Fangs.
I'm aware that you're trying to get some of that power on her poison back but by channeling all of its potential into her E, you're just making things worse for her. You already halved her poison-damage before, and now you're expecting her to go into short range for the entirety of the game just for some questionable compensation that isn't even mana-efficient for her? She has zero safety which is unheard of for any other hypercarry in the game. Her ultimate is delayed and can easily be avoided, she has no gapclosers/reliable escape-tools and her damage-output is far too unreliable since it requires you to poison a target first to enable her E-spam.
No matter how low her cooldowns may get later on, they're still too high to make it work once you're in a teamfight. Now add some reoccuring mobility creep to the mix and you're bound to miss some of those skillshots. That's more than enough to render her useless and even helpless in a teamfight - you leave her absolutely zero room for mistakes. Try comparing this performance to that of actual hypercarries like Vayne or Tristana who can actually peel for themselves and aren't hindered by having to land skillshots. Also they aren't restricted by absurd manacosts since all of their damage comes from auto-attacks alone which also allows them to change their target anytime without having to fullfill any conditions.
Cassiopeia will never truly function as a hypercarry as long as you keep her focus on having to land short range Twin Fangs while constantly exposing herself to the entire enemy team. She's a literal glasscannon, in the end it doesn't matter how fed you are. And even then she can't melt tanks fast enough once they stick to her, that's all it takes to remove her from the map. Not a single mistake goes unpunished in the lategame (you know, that stage of the game where she's supposed to become relevant), infact it's enough to lose an entire game. And just because her Flash happened to be on cooldown.
If you expect me to jump through so many hoops just to get that far, you better make her endgame worthwhile. Enemies have a much easier time shutting her down once they approach their own lategame (pretty much the opposite of what you aimed for) where all it takes it a single cc to blow someone up. You see the problem there?
Your hypercarry fantasy has far too many flaws to actually work. You NEED to shift your focus on her other abilities if you expect her to survive in a lategame environment. I strongly suggest reading Grand Eleven's post on how to approach this matter so that she may become a monster again, capable of melting entire teams. Now that's what you'd expect from an actual hypercarry, wouldn't you agree?