Small Lee Sin change that will be a step in the right direction to balance him.
His W second active should be merged with the first active, the skill should become:
First cast: Lee Sin dashes to the target ally and shields them and himself, while the shield persist, both lee and his ally gain bonus lifesteal and spellvamp.
New Second cast: Lee Sin dashes to an enemy dealing damage (scales with AD) and slighty knocking them back (enough to stop channels).
This change will let lee break overpowered channels without having to burn his ult. This will also make his assassinations more reliable by letting him easily W to an enemy to hit a point blank Q - E - R - Q again to finish.
I believe this change is for the better as it will separate good
from great 
without having to burn his ult.