Isnt it funny how boards have no idea what are talking about? aka a view on state of the pre season)
The top 10 mid lane win rates are all occupied by mages atm (multiple of them with 55% wr), "but ap is so weak!"
"tanks are so trash i die in 1 second wtf" and yet the top wr for top and jungle are respectively maokai and rammus (at 55% and 56%), to add most of the tanks are above 52% and seen increases on their WR compared to last patch.
"assassins are so op so much dmg" zed is just barely at 50% (with a few like fizz being at 52%), and so are the other assassins.
Bruisers overall dropped btw 2~10% in winrates because fervor got deleted with no compensation (eg darius at 46%, riven at 48%) " but shut up tanks are SOOO WEAAAAK".
Basically the current actual state of the game :
Mid lane mages are extremely strong atm because aery is broken and everyone has -12 mr, assassins seem playable again but they still fall off a cliff if they dont end the game in 15~20 mins.
Tanks are broken because nobody can lane against them after first/second back anymore since theres no more fervor or anti tank runes, have fun playing a bruiser top lane against a tank who will not only auto win lane as soon as he backs with 1000 gold, but will massively outscale you.
Bruisers are shit because they cant lane against tanks and they get outscaled by everyone on the map (with the only exception being yorick at 56% win rate because he can cheese towers, since those are just in a pathetic state atm).
Adcs and support are a bit less strong, specially late game oriented as they just lose lane too hard and get snowballed on, janna right now is at 48% and with good reason, she really isnt good at all atm (too weak in lane and why bother when you can just play sona and have a 10 times better lane while being a late game monster aswell?)
Sona and ezreal are both completely busted aswell bot lane (wrs : ez at 55%, sona at 58% before the hotfix), specially sona the champ is completely disgusting early lane bully that can chunk you 30% hp in 1 Q aa lvl 1 while scaling better than janna lmao.
Now for the keystone ranking:
Most broken keystones, that need nerfs, champs that can effectively abuse these are pretty much automatically top tier : Aery, Klepto.
Strong keystones : PtA, grasp, aftershock.
Useful/situational keystones : lethal tempo (on hyper carries), electrocute (assassins), guardian (melee supports), predator (for junglers), comet on very specific champs (its worse than aery overall on mages without cc or long cd spells).
Everything else is just mediocre (other than a few VERY niche cases like singed with spellbook)