I disagree, and so do the stats - http://champion.gg/champion/Cassiopeia
Even if she had amazing stats, that doesn't change the fact that she feels terrible to play now after the plethora of nerfs. Early game anything and everything runs her over, because if you fight back your mana bar will be empty in literally one exchange. Just one.
That'd be fine if she scaled into something amazing, but the bullshit walls and conditions are unrealistic for her current state. So that great scaling that she's supposed to have doesn't really exist.
And to answer the OP: That rework was nothing more than a gutting to silence the whiners. It never reached the PBE and Lee Sin is trash anyway.