My experience in Season 6 and now is that I either get gold and scale so hard I can 1v2 with ease, or I get denied gold early and I'm just dead weight to my team.
I feel like Fiora is a bit too feast-or-famine at the moment, but most of that is just due to her kinda lackluster laning. Her early damage is almost non-existent unless she procs a Vital, but that forces her into melee range and a lot of her top lane opponents are Juggernauts who can hit harder than her while also being tankier than her (because more of her power is in mobility) or are ranged and diving them to proc a Vital would put Fiora massively out of position and take tons of minion aggro.
Fiora just seems like she has no real fall-back options if her lane opponent is strong enough to poke her out of lane and/or zone her from farm. She can only sustain through poke by proc'ing Vitals, which only really works when she's ahead or at least even, and has no means of ranged last-hitting or wave clear to fall back on. She can hit something with her 30 sec W but that seems like a terrible option both for the long cooldown and it being her only defensive tool.
Akali is glass cannon melee and she can at least fall back on her ranged Q to last-hit and try not to feed.
Katarina has her ranged Q also.
Yasuo's Q has some range and he also has solid wave-clear with his E.
Riven has AoE on her Q and W that she can clear waves with, and can farm and escape with E as a fall-back pattern.
Tryndamere is pretty unhealthy and in need of a rework but has wave-clear on his E and can heal off some poke with his Q.
Master Yi can pretty safely farm with his Q as a fall-back and also has a good heal on his W.
Out of all the glass cannon melee champs, all of them but Fiora can at least sort of farm and all of them but Fiora and Yi are manaless.
I love playing Fiora as a split-push Goddess, but goddamn getting there can be worse than having teeth pulled sometimes.