Look at the bigger picture, a lot of things were changed. And to be completely honest, Fox-Fire felt really underwhelming in Season 4.
- [Buff] Fox-Fire's targeting system has been improved and will now attempt to acquire a new target if the original target is going to die from other Fox-Fires
- [Fix] Casting Fox-Fire no longer interferes with Ahri's basic attack animation
- [Buff] Slightly reduced the time between spell cast and the missile firing
- [Fix] Fixed a rare bug where Ahri's third Fox-Fire wouldn't deal damage while her passive was active
- [Revert]
40/65/90/115/140 magic damage ⇒ 50/80/110/140/170 magic damage
- [Buff] Fox-Fire's rotation speed has been increased by ~30%. This means if Ahri's hitting a champion with Fox-Fire at maximum range, she won't have to wait as long for her other Fox-Fires to rotate closer.
- [Nerf] ACQUISITION RANGE 650 ⇒ 550
Since Fox-Fire's range is calculated from the foxfire to her target, 550 Acquisition range is roughly equal to 600 skill range (i.e.: Spirit Rush), slightly shorter than a 550 range basic attack (it's complicated).
They lowered the acquisition range, but made the Fox-Fires rotate faster. Even before the change, you needed to walk dangerously close to your opponent to use all 3 charges. Overall, it's easier to use all 3 Fox-Fires reliably at the cost of losing some cheap reliable ~700 range harass.