Passive: the reduced mana costs are very nice, and mean that she gets to play much more proactively in lane, but it does feel very lackluster and it took a minigame that was fun to manage. Would rather have seen a slight cost reduction on q/e and left it the same, but it's fine.
Q: The healing is very strong, and with how much more she can spam abilities it makes it very easy to remain at full health in lane. I really miss the movement speed on her. Really brings to light the argument of removing fun elements to the game in order for "viability".
W: This has been a real killer for me... I know you're trying to slow the damage down to give opponents more time to react, but this is a little much. There really isn't any way to get the damage amp on this ability outside of prepping it in fog of war. It makes it very obvious when the Ahri player wants to go in for a trade, so enemies just opt out and you're out the mana. I don't use this in lane anymore, which is annoying since it was a very good tool to pick up cs (not a big deal, quality of life really). It stylistically takes from the champion as well, she's graceful and cunning. The ability as is, is clunky and slow. Not a fan of this change at all =S I understand why it's there though... Unsure a bit on this one.
E: Not as overbearing as I feared. It's pretty in line with the rest of the champions powerlevels. Could become an issue if her w is made better though.
R: No change
TL;DR passive is lackluster, but useful: I like it enough
Q healing is very strong: overtuned?
W I don't like it: the changes hurt lane pretty bad: Necessary evil; or hit way too hard...
E Strong, but not gamebreaking: Good
Edit: why not make the w a charging mechanic. Where it increases range/damage the longer you hold it down, but only up to the current numbers? slows it down, but keeps all of the previous utility.