Fiora's early game is decent for new players but stronger than intended for experienced players. Simply because more experienced players have already learned how to maximize her damage output and remain safe even without Vitals and Vitals are supposed to be her early game boost to damage and sustain.
Fiora has been buffed in the past because her early game was weaker than intended.
And that was a time where top laners did a number on her and she couldn't fight them back properly. So in patch 6.14, here's the reasoning behind her buffs:
#Fiora (6.14)
Passive heals more. Q scaling increased at early levels.
Fiora’s a devastating side-lane duelist when given the appropriate support, but she’s struggling to find success outside of the professional scene. As mentioned with Azir above, it’s important for late-game powerhouses to have early windows of vulnerability, but the degree to which Fiora's being punished at early levels is just a bit too high. We’re improving Fiora’s early trade potential to help tip the scales in her favor when the Grand Duelist starts making the right moves.
Passive - Duelist's Dance
HEALTH ON VITAL HIT 25-110 (at levels 1-18) ⇒ 30-115 (at levels 1-18)
Q - Lunge
RATIO 0.55/0.7/0.85/1/1.15 bonus attack damage ⇒ 0.95/1/1.05/1.1/1.15 bonus attack damage
Fiora did need help to her laning in 6.14 so this was an appropriate call to make but since top lane stats have been reduced with the tank update, Fiora naturally rose to the top due to this buff that happened before all of this.
However, fully reverting buffs to Lunge might reduce her poke damage (which is intended) but it also may make her CSing harder so this is why i proposed half the reverts first. The point of this reduction is to reduce her poking strength to appropriate levels, not make her an overall worse top laner because some people want to see her gutted. Fiora's supposed to kick your ass in the late game (where she has her items) so there're no problems there in my opinion
She's a fair champion that takes quite a bit of skill to play because her Vitals are her minigame that she has to play around.
The thing about GP is that one Rioter (before the % armor pen pass) already commented that GP's barrels might be ignoring way too much armor which is resulting in an extremely strong late game, compared to how hard he can be shafted early. The thing about scaling champions is if you manage to keep them down, you should delay their spikes for quite a bit.
They shouldn't start beating your ass down after you've given them hell for 20 minutes of the game, all after a single item purchase where they manage to round up the minimal stats they need in order to be relevant and then start racking up pentakills, before the game has been practically a 4v5 - up to that point.
I'm not sure if that's still on their to-do list but this was their comment at that time. I can even agree that GP can sometimes feel so overbearing with just one barrel that chunks you for ~80% HP, with only 3 items (probably Youmuu's, Trinity Force and IE). That's only half of his build.