The problem of Yi
I brought this up in another discussion and felt there needed to be a thread specifically targeted at this subject. I'll expand on each of the problems, but I'll start by identifying them.
So first of all There is an inherent problem in his kit, he has the damage output of a melee assassin with the survivability of a more tanky fighter/bruiser. Second problem is he has no real place in the game atm except for abusing low elo play style. Once you hit a certain threshold Yi just doesn't bring anything to the game anymore. Every attempt to really address this champion as a whole failed because these attempts didn't really consider the identity of Yi, what he should do as opposed to what he does. It usually results in him just being way too powerful or too weak to even exist.
On the problem of his kit and place in the game, it can all be traced to one ability, his W. In his current iteration at low elo he can go in gank a lane do what Yi is designed to do but then can just heal up and do more regardless of whether there is an enemy nearby or not. The damage reduction buff on top of the heal itself makes him just a skilless champion that can get away with being greedy. In high elo he has no way to effectively get in to successfully gank, sure you can say he has his ult, but the vision game in high elo is very effective at dissuading Yi ganks. This makes him less impactful on the pace of the game. Sure he can power farm his and the enemy jungle fairly safely as long as his team is doing fine, but in high elo if the team is doing poorly Yi is just useless.
On the problem of addressing Yi, when Yi gets powerful he almost always sees a meaningful nerf: AP Yi, Feral Flare Yi, etc. Then almost immediately after, the reasons he was so strong get nerfed. Feral Flare removed, even removing the atk. speed from ghost blade hit Yi hard. When the items get nerfed Yi sees no compensational buff to make up for it. Not sure if this is just an over-sight or intentional but it is really detrimental to Yi players.
What I propose will actually solve the majority of Yi's problems fairly simply. If Yi's current W was removed, then replaced with something like a three charge dash that applies an auto-attack to enemies hit that applies on hit and lowers the cooldown of his Q like regular auto-attacks it will give him identity, and more meaningful ways to gank, especially since Yi is so auto-attack focused and gets a lot out of life steal items. Instead of just popping W to wait out Q duration while healing up and taking less damage Yi players can dodge incoming retaliation and still get the Q back up in order to fight. It gives skilled players more options and makes him more punishable at lower elo. It also synergizes well with the fantasy of a very fast swordsman that intends to kill you fast.
Heal, AD reduction, R
W
Passive, W
Q, W
W
E
W

in having no CC but is completely melee and his abilities do shit for damage.