This wouldve been a good battle.
Shino is an undercover genius who has shown enough in part 1 which hints that he should take this. Afterall he is a mid to long range fighter. He also has great defence in close combat as seen against kankuro.
Lee's speed and gates would cause him great trouble. He has to and can beat lee before lee decides to use his gates. If he hasnt won the fight before lee activates his gates, shino is getting destroyed.
Do i believe shino can beat lee before he decides to use his gates?, yes therefore shino takes this with mid to high difficulty