Yes I main Lee Sin and yes he is overtuned.
It used to be his early game power was reasonable enough due to his subpar late game. There have been 3 buffs since I started maining Lee. The % max health damage added to his ult if his target collides with other enemies, the shield strength on W, and the spell vamp/life steal strength on W. All of these changes combined with the new jungle pathing of Red+Krugs=lvl 3 gank cheese have caused Lee to be quite a pain. Of course he still takes considerable skill to play to his full potential and to succeed in higher elos, but he takes less skill than ever to succeed with in general. Whenever I play Lee now it almost feels like I'm cheating because I know if the enemy laners push, I will gank and win. Now I don't have much in the way of nerf suggestions. His ultimate does a fuckton of damage due to its high base damage and ridiculous bonus AD scaling so Riot could probably hit him there.