Since you're so hostile to general matchup advice, I took the liberty of looking deep at the stats from the single game you're complaining so much about
First off, you're lying about having been ahead. According to lolking, Fiora was ahead of you in farm, gold, and experience at all points of the game. Even if you had gotten kills on her, she still had a lead on you.
You bought an executioner's calling before finishing your Shiv. That's a mistake. Her healing isn't anywhere near significant enough that early on for it to be worth the 800 gold for grievous wounds, and Shiv amplifies your power in short trades - which is what you should be going for since she has Fervor.
Now, Shiv itself is questionable - most people go PD for that 12% damage reduction, but I'm not a Yasuo main so I digress - but delaying your powerspike is not good in a counter matchup like that, especially when Fiora's powerspike items are much more expensive.
You also bought Iceborn Gauntlet, which is... I'm not even going to act like there's a situation where you should be buying that on Yasuo. It's trash. It's really, really fucking bad. Half its gold value is in mana and CDR - useless stats on Yasuo. You spent a BF Sword's worth of gold on mana and cooldown reduction on a fucking Yasuo. Do you think the armor is worth it? Why not Deadman's then? That shit gives you health and movement speed. Useful stats! Randuins! It reduces their fucking attack speed and makes you take less damage from her crit! If you were going to get a defensive item, why not those? The Spellblade effect wouldn't have even been useful in that game. You don't want to stick to her. It's not going to keep her from sticking to you. It's not a significant amount of damage. So why? What made you look at that item in the store and think "Man, that's the item that will surely make me get back into this game"?
You got countered and lost because you don't know how to win the matchup. Don't go on the forums and complain and ask for nerfs. Just makes you sound like a sore fuckimg loser.