Ahri's speed boost should be on Foxfire
Most of her spells have a defined purpose, and feel like you're getting something out of it when you put a point in it.
Her passive is good sustain in the laning phase. Not overbearing, but you certainly feel it when you are playing her. Her Q is her main damage spell. Her E lets her land her entire Q. Her R gives her an escape and helps land her E.
And then there's foxfire, whose purpose is to be another instance of the damage from her ult. In the words of Gordon Ramsay, "It's Bland".
Adding a speed boost to Ahri's kit was a great idea, and made her feel a lot more agile.
It added spice, but Q already felt good. Her W needs that flavor much more than Q.
here you go
W fox fire is there to land heaps of 