Stashu. Can you please just start from scratch?
Even with the PBE "buffs" the issue remains. It's also less about her powerlevel. It's about her gameplay. Especially the passive.
Cassiopeia has become so horribly unfun to play. With the PBE changes Cassiopeia feels even more dull to play than on live. Hitting a Q is so unrewarding! Unless you hit an E it does even LESS damage than it does live. Landing a Q (playerskill) is near useless unless it's followed up by your enemy making a mistake (not within the influence of your playerskill). Her W is a JOKE. High Cooldown. Low initial radius. Horrible damage. The damage nerf to her ultimate turned one of the most high risk/high reward skills into trash. And her E has become horribly overloaded.
JUST PLEASE. Your concept went horribly wrong. Don't try to a fix a sinking ship by stuffing the holes with cotton balls. Just get rid of this concept all together. I beg you!
EDIT: On a sidenote. Cassiopeia's popularity is at an all time low. She is the 2nd least popular champion ingame. There are more than 120 champions the community would take rather than her. http://www.lolking.net/champions/ http://www.leagueofgraphs.com/champions/stats/by-global-popularity