Why I have a problem with Fiora

Q cost - 20/25/30/35/40 mana

Q Cooldown - 16/14/12/10/8

Mana Regen P5S - 8 (+0.7 per level)

Mana- 300 (+40 per level)

Q refunds 60% of the cooldown when it hits.

Q base damage - 65/75/85/95/105

At Level 1: If every Q hits, the cooldown would be 9.6 seconds. In that 9.6 seconds, you would regenerate 15.36 mana. At this rate, it would take 64 uses of Q, back to back, hitting every single one, to run out of mana. This is equivalent to 10 minutes and 20.4 seconds. This means that, on average, Fiora will do 3,328 total damage with her Q without running out of mana (taking into account that the average base armor is ~25, and assuming that neither Fiora nor her target have any masteries or runes)

The earliest Fiora could max her Q is Level 9. At max level, the cooldown on her Q is 4.8 seconds if you hit every one. The mana cost on her Q at this point is 40 mana. During the cooldown of her Q, she would regenerate 13.1 mana. At this rate, it would take 23 uses of Q, back to back, hitting every one, to run out of mana. This is equivalent to 1 minute and 50.4 seconds. (Too lazy to do the math for base armor at level 9... just know that the damage is somewhere between 3328 and 2415, which is the average damage at level 18.)

What I'm aiming to prove here is that Fiora's laning is oppressive. She's able to harass you away from CS no matter what melee you're playing, simply because she had no penalty for using Q recklessly. Up her mana costs to, say, 70, and scaling down to 30. These numbers might be off, just a suggestion off the top of my head. The mana costs are too low for the harass she's able to provide, and there is literally no penalty for just spamming it to keep the enemy laner off the minion wave.