Diana, over 50% winrate, high damage big burst combo. Akali, kind of like Diana, she pretty much 1 shots if the game extends to 25-30 mins. Katarina, even though her winrate is weak atm, if you are patient, farm and wait out the first 15 mins you can still snowball pretty hard.
Talon
As a Rengar main, I felt the changes hard. They gutted his early game with Youmuu's, Tiamat, and Hydra changes. Even his mid game because I'm always missing 10% cdr out of 40% until i get a triforce since they nerfed Lucidity and removed CDR from early tier in masteries. And this is for Jungle Rengar btw, which is my main. I have no idea how all the Top Rengar mains are doing. I also fucking hate how late into the game I need to be for any sort of crit.
Ghostblade, Infinity Edge and Ravenous Hydra changes have destroyed most AD-based assassins.
Meanwhile, the MetaGame is focused around snowballing and early-game champions, as such; Renekton, Lee Sin have become incredibly powerful champions - Tryndamere is a nightmare with how good critical strike has become (and Yasuo), and ADCs can almost never be assassinated anymore due to assassins basically being phased out.
On top of all that, the "Late Game" doesn't really happen anymore, save a few close games - which has invalidated a lot of the AP Casters (both mid, and Jungle) - as if that wasn't enough - the cost of all AP items have been increased between ~70-250 Gold, while all AD items have had their costs reduced.
ADCs and AD Champions in general can receive up to 56% Armour Penetration, which makes having an AP champion almost pointless - unless you're Veigar.
Oh, and the Zhonya's nerf - before I forget, which hurt LeBlanc, Fizz & Kassadin so much.
