Fiora doesn't need buffs. She deals way too much damage early via vitals and spammable low-mana-cost q. I've said for over half a season now they need to change her ult to do PHYSICAL damage instead of TRUE damage or else cut the ult damage literally in half.
Riven - I don't play her - she seems like she has a hard time trading until she gets some good item components though.
Camille - unsure; don't play her. Probably better to revisit her durability vs damage output as she's supposed to split the difference between a jax/fiora and a darius/renekton (splitpush squishier champ vs teamfight damage champ).
Renekton - is actually underpowered with how strong tanks are AND with the buffs to other bruisers and duelists. Garen got tons of free armor pen on his e AND stronger passive. Fiora could already beat you early if you make ANY mistakes and definitely outscales you. Nasus got PERCENT ARMOR PEN on his e and more spammable q during ult vastly increasing his dps at lvl 6+. Until renekton gets cleaver, he basically does less damage than most tanks in trades and must rely on q spam to heal up damage more than the enemy tank can - made harder due to bramble vest. Another issue with renekton is his healing is reliant on hitting a group of targets (generally minion wave and maybe enemy champ too). While this means he can heal up without hitting an enemy champ (compared to darius or fiora who must q an enemy champ), it also means he gets less healing when not hitting a full minion wave PLUS enemy champ. If you look at even his base stats - they aren't stronger than many other toplaners either, and the scaling is weaker than any other toplaner. He is literally only viable due to the excellent synergy of hit basic abilities - which allow him to get very favorable short trades. TLDR - yes he needs a buff.
Options: 1. buff early game - more base damage and attack speed, more base resistances, or something like that. I personally dislike the option because it would make him super oppressive to lane against when he CAN already feel like that now sometimes.
2. Give him the nasus treatment - nasus ult used to give just resistances and some dps. They buffed ult to give hp too - stealing some of renekton's thunder. So... Give renekton ult some resistances. Like 20/40/60 armor and 10/20/40 mr. This wouldn't make him overly more oppressive in lane and it WOULD help him become a tanky teamfighter which Riot acts like they want him to be (although his stats don't allow this currently - he can only SEEM that way if ahead of the game by about 1 full item).
3. Other stuff... e cd is way too long; should be about half of what it is. W stun duration should level up as you put more points in the ability especially since it temporarily "roots" renekton too - unlike many other champs' stuns. This would actually be great too because w is ranked up last - meaning it won't hurt opponents in the laning phase, but will come into play in mid/late game splitpushing and teamfighting. 0.75-1.5 sec stun at rank 1. Increasing to 1.5-2 sec stun at rank 5 w. Give better armor shred option than his e - because we all know how little and how awkward it can be to use empowered e... very awkward.
Jayce - too damn strong early, not good enough late. Maybe make e,q combo scale better. Even buff w damage scaling. Could drop a bit of damage on melee form to compensate if needed.
Kled - yeah haven't seen him in a long time. I don't know that he NEEDS a buff, but he's definitely not broken. And with the cleaver titanic j4 build still being decently popular, you would have thought kled (who also builds like that) would be more common pick. So some small buff is probably ok.
Jax - uh... no. Champ has way too much free damage and durability in his kit as is. Literally the only reason he isn't top-tier is because he's hard to learn. But if mastered, he's top tier or better. Can teamfight AND splitpush effectively too when properly itemized. Can win at all stages of game. That's not just some lowly gold's opinion either - that's the opinion of many ex-pro toplaners - at least the hard-to-learn but broken part.