Come on, let's be honest with ourselves Lee Sin is not as dominant as he used to be in order to afraid even buffing his shield from safeguard or something. The days where Lee Sin defined the jungle no longer exist. With all that development around the jungle, a ton of junglers are finding a lot of sucess and they are even outclassing him at the moment, in terms of clear speed. Hell even on pbe they are increasing his shield early on which in my eyes shows that if Lee Sin is getting buffed where he's supposed to be strong(early game), it means that something goes wrong his the champion. So, I strongly recommend doing a meaningfull buff to his late game where he struggles the most. A tank jungler not only has a lot more better clears than him and stays healthy throught out them, he has cc and supportive capabilities to peel for his team and especially his carries, while being a lot easier to play. Someone like sej has a passive that gives her a ton of resistances, aoes slows and targeted stuns. Someone like zac has an aoe knockback and stun(his e) and the unique cc effects to his q and his ultimate(displacing targets in general). Lee Sin has the ability to shield an ally for 2 seconds, an unreliable slow from his e that fades over its duration and an ultimate that I you don't play him like Gripex u only knock away enemies from your allies and then die and if he happens to snowball, he falls of quickly after levels 9 and 10. Someone like shaco can snowball and still be a threat through out mid and late game. Don't get me wrong, I respect the tools that Lee has on his kit and I know what he did in the past and what he's capable of doing if overbuffed. If he's played to perfection he's good, but the unreability that he kit has right now doesn't even make him a competitive pick. And plz end this joke Lee is too strong because he's versatile AND ALL THAT BULLSHIT. If a good player ruined your game because u couldn't cc during his incec or u didn't dodge his q and he rekt u completely doesn't mean that he's a broken champion. I especially refer to higher elo players that should probably be plastic 7 not diamond 1 if they say that thing.
I strongly recommend the following buffs:
Shield duration on safeguard increased from 2 secs at all ranks to 2/2.5/3/3.5/4 secs when he casts it to an ally.
Cripple has an attack speed slow added at level 12 which is as much as 20% and scales to 60% all the way until level 16 and that attack speed slow will proc on crippled targets only if one of your allies damage them, even when the are marked with the reveal by tempest(the slow will occur when u cast cripple). Max duration 4 secs. The AS slow fades over its duration.
That way he will be more impactfull in terms of utility into the late game and he will be able to stay up against other junglers.