Fiora is D tier for a really long time. The higher the elo you go the useless fiora is!
** Fiora is D tier for a really long time. (2 years out of the meta, 1 year of being D tier) She can only one vs one and nothing else currently!** https://u.gg/lol/tier-list/?role=top&rank=diamond_plus
There is so much damage in the game that the buff that fiora needs, is a buff to her w for late game. So not more movement speed, not some more early game duel power.
Here is a suggestion of a buff for fiora:
Everytime you get a kill with fiora, her parry cooldown get refunded by 10%. The cooldown refunded stacks, so when fiora gets; double kill: total of 20% cooldown refunded, triple kill: total of 30% cooldown refunded, and the list goes on...