Design priciples and the Ahri change
For those not up to date on PBE balancing:
Recently a change to Ahri's charm was proposed on the PBE, where the charm would no longer interrupt dashes (the entire PBE update can be found here: http://www.surrenderat20.net/2016/02/216-pbe-update.html)
The Ahri change: "Ahri Charm (E) [SmashGizmo noted Ahri's Charm will not interrupt dashes anymore.]"
The proposed changes seem like they are a noticeable step away from some of the design principles we've been told Riot do design and balancing around, namely "retaining what is unique about a champion and strengthening those elements" and "promoting counterplay".
Starting with the counterplay aspect, removing the interrupt on dashes will only serve to remove Ahri players ability to counterplay others (looking at you 
, 
& 
) without really impacting the strength she currently has.
At the moment Ahri is too strong (even as someone who is benefiting from her strength I am willing to recognize that part), however her strength is not that she's too good in the hands of dedicated Ahri players who have experience using her charm in efficient ways or even just those who are using her skillshots well, her strenght is that she's currently far too safe with too much of an ability to do damage without really putting her self at risk (throw q and sprint to safety at a pace even Rammus can admire), weakening a skillshot which prevents other players dashes won't give Ahri any more of a defined weakness than she currently has but rather strengthen a core group of champions against her at all times while leaving most of the champions she's already too good against in the same state they already are.
As for designing champions around their core identities, I might have a different opinion on who Ahri is than what Riot's balancing team does, but to me she's always been a kite mage (even when she was assassinating targets left and right with dfg, her kit always allowed for her to keep moving around after you'd killed some poor defenseless sod), and the core aspect of just how enjoyable she is in that role is her charm.
Even more so than her ultimate, her charm is the aspect of her kit that has always made her satisfying to play, as it forces you to always keep moving and positioning yourself in such a way that you will have a clear shot at your opponent, whether you want to land a charm to go in or you want to stop that pesky from blowing you up with a quick q-w combo. Moving around minions and monsters and keeping track of where your opponent will come from so you can prevent that stun (), displacement (
) or burst (
) is when you feel like you get rewarded for having put time into Ahri, and why dying as Ahri leaves you reflecting on how, maybe if you just saved your charm to stop that 
diving at you from a bush instead of trying to kill that 
, maybe things would have turned out differently.
If you want to change Ahri, and keep her identity intact as the most engaging kite mage in the game, put more of her strength into landing her skillshots.
Examples of changes I would recommend before killing the most engaging aspect of her kit (or even most if not all combinations of these):
-
Make her q only give movement speed when it hits a champion: making it harder to dodge around while using her q as waveclear and forcing her to think more carefully about where she throws it when kiting
-
Remove the movement speed on her q outright: If she's too good at getting out of sticky situations as she is then remove the aspect that lets her be consistently slippery, while leaving her ability to get out of tricky situations by carefully choosing a target.
-
Hit the damage on her W and R (probably alongside a nerf to q's move speed): Her Q and E are great examples of Ahri being rewarded for moving correctly, hitting both directions of Q or keeping a clear line between you and your soon to be love slave is hugely satisfying, while Fox-fire and Spirit rush's far simpler premise of: get close is a lot less rewarding for Ahri players and harder to play around for her opponents.
-
Bring back the damage increase on landing charm (obviously coupled with lower damage on everything else as compensation): Putting more of her strength into landing her charm, would create a clearer window of opportunity for her opponent when she misses her charm, while still rewarding Ahri players who consistently hit their targets
Just please don't take away the most engaging aspect of my favorite champion.
