The real problem with Lee Sin that people are missing.
1140 + 480% bonus AD scaling on his entire kit. Oh and lets not forget the 8 % of missing health on 2nd cast of Resonating Strike
So all this on top of excellent sustain because he has a shield on top of spellvamp and lifesteal on his w. Oh and the BS root on his ult that makes you unable to react.
So he can w to a ward near you, spam his ult and E on you, and since his Ult does some pretty stupid damage for a fighter, his Q does ridiculous damage on the 2nd cast.
TL;DR: Get rid of the Missing health ratio on his Q. It just does way too much damage.