**EDIT FOR CLARIFICATION PURPOSES:**
Lee Sin's W, Iron Will, currently gives him 5/10/15/20/25% Lifesteal and Spellvamp for 4 seconds dependent on rank. I am suggesting we remove Spell Vamp so he can only heal from autoattacks during his W. Potentially increase the Lifesteal to 10/15/20/25/30% or 15/20/25/30/35% if it seems too drastic to take away the spell vamp
To balance Lee Sin I think we need to take away certain random bonuses instead of focusing on nerfing his core gameplay.
He doesn't need Spell Vamp since he already has lifesteal, although this would impact some of his dueling and jungle which is honestly fine given how well he can gank and teamfight at pretty much any point in the game.