Ahri's whole lane pattern is just stupid.
The problem with her is similar to Leblanc's where she has strong long ranged CC on top of Ridiculous non conditional Mobility
At level 6, an Ahri that doesn't suck can basically all in you at any point in lane and there is almost nothing you can do unless they are bad.
And her pre-6 Has her throwing Q's constantly with 0 way for you to retaliate because of the Speedboost it gives her. In lane, her Ulti also acts as an effective second flash that you have to try to burn for jungle ganks.
She has the mobility and burst of an assassin with the CC and Burst pattern of a Burst Mage. Even MORE so than Leblanc.
Getting hit with 1 Charm means you are dead, which is fine on champs like Lux , Xerath etc who have to often risk positioning due to their immobility unless they see an opening, but Ahri usurps this weakness all together.
The first thing I would look into changing in her kit is her passive. it just feels like it is only there as a relic of the past and can make laning against her even more needlessly frustrating because what little harass you magically can get on her is erased just by her constantly harassing and running away with Q in lane.
I personally would change it all together, but for the sake of small changes, lets make it need less stacks to heal her , but only stack when she hits an enemy champion.
The second is I want her Q to require she actually hit an enemy champion to get the MS.
This way, she is punishable if she misses and rewarded if she lands it.