Lee Sin is popular...not sure if broken...
Given how Lee Sin's stats go from a 47% win rate in Bronzie-Bayou to about 46% in the Diamond Dynasty, can we really say he needs...nerfing?
Like, I know he's popular, but that's due to the LCS boosting his popularity. He's used in the LCS because he's highly versatile, pressures early, and his main drawback is difficulty, which a pro jungler probably gives less than even two atoms of shits about. Since he's used in the LCS, more people see how strong he can be at the top of his skill ceiling and play him. They don't realize that Lee is still really hard to play efficiently and bomb it, thus ruining everything and losing. This is what I assume, anyway, given his HUGE popularity and his pretty shit showings as far as wins goes. Broken would probably look more like Janna than anything else, who has a pretty high play right and near a 55% win rate at the same time in both Plat and Diamond.
I think Lee's issue is that he's TOO general. Nerfing him, however, would probably be unfair to the champ outside of very minor things like a decrease in his natural movement speed. Seriously...why can he ward hop and run that damn fast? He's fucking blind...how does he run this fast?
