Yes, he does indeed have a bit of everything, but at the same time that makes him a jack of all trades and a master of none. If he builds Damage, he falls off. If he doesn't get ahead by a lot and win the game pre 20-minutes, he's already falled off. If he builds tank, he's not doing damage and is nothing but something that can get in and kick someone back. His insane scalings are not that insane: It's bonus AD, not total. The thing about Lee is that there is so little room for error unless the enemy team is outright bad. Kassadin is a completely different story in the means of he is a late game champion. He does not win lane, he's not intended to. He's supposed to survive until 6 and then come back. He's almost always starved for farm unless the enemy is like Veigar who is doing nearly the same thing.
On another note, Lee is a high skill cap champion who deserves the versitility. If you can play him to the perfection that he demands to be played at in higher elos, not even Challenger, but something other than the bronze to gold most of us are in, then there's no reason for it to not be rewarded. Otherwise there would be no reason to play the champion.
All this salt to do with Lee Sin needs to stop because this isn't the first time he's been brought up on Reborn.