Long post, assessing each lane atm with focus on win and play rates in low, high elo games, as well as worlds.
First some stats on some the biggest issues:
Mid laners Gold+: Garen (57%), Pyke (55%)
Garen has a 57% winrate. Pyke has a 55% win rate. Not only should a champion never, EVER be this far above the crowd - these champions are not mid lane champions. Or at least, they aren't marketed as such. Now admittedly, Garen's winrate drops to 50% in high elo and Pyke steadies to 53% in high elo. They still aren't even below 50% where the best of the best are playing. Pyke still boasts a formidable winrate as support, and Garen steadies to 55% or 50% winrate top lane as well. (Reference A)
Top Lane: Biggest issues are Kayle, consistently high winrate (53%) in both high and low elo, minimal risk, and abuses Klepto far too easily. Pantheon consistently dominant numbers in low and high elos (53%), 100% pick/ban in worlds this year. (Reference B)
Support: Shaco at 56% low elo and 53% high elo winrate. (Reference C)
ADC: Ashe (54%/52%) winrates while possessing one the safest laning phases, dominant poke, and a literal game-changing ultimate that she need not even be present to utilize. Kaisa is selected in 40% of games. That's right, nearly half games ever have Kaisa in it and 11% ban rate sets it to either 50% pick/ban. The next champion to even come close is Lee Sin at a 25% pick rate, 10% ban rate. Near 100% presence in worlds too. Winrate isnt the only important stat when it comes to champion balance. With every other game having a Kaisa presence this obviously means she's far, FAR too easy to play and take paper to reality and you see it: Extremely safe laning phase, the most massive power spike at 3 items and no longer is an AA marksman, typically 1 ability combo +1 AA = death, and ability to get to the backlane far too easily to get the game winning kill no matter the past 20minutes. (Reference D)
Junglers: Almost none of the champs are the same in high / low elos for reference. High Elo has very high skill cap junglers or junglers that a small playerbase makes use of very very well like nidalee khazix and fiddlesticks. Low elo takes very easy champs like mundo and voli and wins lots. I think the jungle is hard to assess because the experience, pathing, and general state of the game is such a cluster-- that its skewed for no fault of the champions themselves. Nunu is the only constant, and its likely because his ganks are far too easy to pull off, far too difficult to avoid, and a failure on Nunu's point very rarely ends in his demise, as well as having two smites for later in the game. (Reference E)
A: This is very annoying to me. The PBE both by players and many videos made, all told you that Garen was busted in his rework. You tried to rework him before and paused because of the backlash. Yet this time you did not listen. I understand Riot is nerfing him next patch, but that isn't the point here. The point is that they don't even listen to PBE'ers, so why have the players test at all? I personally think, other than that issue, you should have a hotfix option for every change you make thats drastic - one that already has potential nerfs to a champion that you can roll out quickly in the event you underestimated a change and be more proactive in doing this. No one should jump 5-7% in their numbers ever under any circumstance and players shouldn't have to suffer under their overpowered shadow for an entire patch, struggling to learn to counter them, all for naught since you typically overnerf and gut them afterward anyway - leaving players on both sides upset. Also, you nerfed Pyke in solo lanes yes somehow his mid win rate in all elos is through the roof and his support is actually lacking now. You marketed him as a support no? Zyra, Janna, etc. got nerfed posthaste when you started seeing them pop up because its very evident you don't like supports in mid lane. Please be consistent. Pyke in general is too safe for mid lane, cannot be killed in mid and spreads gold to his junglers far too much when he/she ganks. In fact, camping the lane rewards way, way more than it should (and roams down bot result in massive lumps of gold). Its Talon on steroids.
B: Kayle might be exacerbated because she counters Garen and hes absurd right now, so her win rate/play rate might be slightly inflated. Still, her curve of power right now is too skewed and shes not weak enough early and far too strong later. Klepto is a major problem, for her and all ranged. Pantheon is busted. I like him and his rework, I truly do. But the stats don't lie and his worlds numbers don't either. Something's got to give.
C: Support Shaco is disgusting. See reference A on how you don't listen to players because I know this was brought up on PBE as well. Your proposed nerf will also just about kill jungle shaco in my opinion and Im a little sick of champions being utterly gutted because you missed the mark in an unintentional lane (that was told to you btw). I like Shaco in the jungle, I admire players that do well with him since I don't play him well - and Im sad that he needs to be nerfed unfairly because of lack of vision on the balance team and the terror that is Support Shaco today.
D: Ashe's dominance in lane is far too uneven, especially having an ult with so much potential as hers, to go along with never losing lane is extremely rough. But she isn't the worst offender in this lane. Holy Kaisa batman. I don't think Ive ever seen a champion with this much play/ban rate, ever. There's 140+ champions yet she is in 50% of games? There is something very, very wrong here - and bot lane is bleeding because of it.
E. Jungle is broken. I don't main junglers but all my friends that do say the same. Most have quit the role entirely. I can't blame a champion this time, and I (Along with others) do not believe preseason 10 proposed changes are going to fix it. If anything, the opposite. Also Nunu a bit too strong.
Finally, lets not forget the losers. There are champions, in their legit roles, nerfed to actual dust with abyssal win rates that aren't touched after, assuredly because of worlds. Braum, and Yuumi (who has been a cluster-- from start to finish - honestly I recommend removing her and trying again), and Poppy are some of the most wounded.
I just watched your Netflix show on how League began because of its close association with its playerbase and loved it. Please listen to them now.
TLDR; Busted champs stay busted for too long. Nerfs and buffs are never on the right mechanics or areas and overcompensating nearly always occurs despite feedback given to you. Please listen to your PBE. Play it safe with reworks, you can also buff damage numbers after, they are the easiest things to change. No champions should have a 50% play rate (Kaisa). No champion should have a 41% win rate (Yuumi). No champion should jump 7-8% outrageously (Garen). And for the love of everything holy fix your Lethality items, Tank items, Rune system, and jungle.