The REAL problem behind J4, Lee Sin, and Zed
Alright, I have been seeing a lot of complaints about these champions (Mostly about zed, with a fair amount of Lee Sin sprinkled in, and a tiny bit of J4 here and there).
People keep saying that the problem with these champions is their kits, and while in some degree this is true, but I honestly think you all are failing to notice the big picture here.
And that picture is:

And what do these 3 items have in common? Thats right, ARMOR PENETRATION.
Honestly, I think these champions are such a massive problem right now simply because Armor Penetration, as it is currently in the game, is downright broken.
You cannot effectively itemize against these champions because ALL of them spam armor penetration, and nearly all of them deal % HP damage (Zed often builds a botrk, Lee Sin's Q does missing HP, Jarvan does % max HP with is autos), this means you cannot build HP against them, and you cannot build armor against them, so effectively you have to blow them up, before they blow you up.
And therein lies the problem. Zed is excellent at eliminating targets without dealing with too much of a counterattack. Lee Sin is crazy mobile and generally builds pretty tank while still dishing out pretty ridiculous amounts of damage (especially early game), Jarvan is generally built bruiser/tank and dishes out a fair amount of damage (although I feel Jarvan's damage is much more manageable than the other 2 mentioned offenders).
In fact, lets have a look at some previous characters that were considered overpowered.
Such as Rengar.
Guess what Rengar was building (and generally still does)?
That's right, Rengar generally builds at least one armor penetration item, (and if he is going full assassin he usually builds all 3).
Then there is Talon....and take a wild guess at what he builds?
See my point?
The problem isn't the champions, the problem is with the fact that armor penetration is so flipping overpowered that it A) makes tanks irrelevant and B) makes squishies SIGNIFICANTLY squishier
You want those champs fixed? Fixed Armor penetration first, THEN have a look at them.
. Just saying.