You say Yi doesn't need a nerf but consider this, AP TF

Pros:
-Able to farm extremely well.
-Does decent damage with Wild Card

Cons:
-Extremely squishy and has low HP if you build him AP
-Easily shut down with almost any CC
-Has only 2 useful fighting abilities instead of 5 no matter how you build him
-He is generally only useful to clean up at end of fights
-He has to be fed to be effective
-All of his skills are visible before they are used
-Shut down in any decently experienced ranked game
-Generally a pretty weak late game
-Slow moving skill shot poke
-No health sustain
-Hybrid builds are inifective

and you're saying that AP Yi is an on par balanced champion?
Also Yi's only ap scaling damage skill does reset if he gets a kill with his ultimate active, it's not a skill shot but can still easily hit multiple tagets along with having has extremely high damage.

Honestly what they need to do is make an item that you can buy which can inturrupt a channled skill. I mean something like urgot, malzahar, or ww ult are powerful... but buy a QSS and they are made almost useless if used on you. Why not give a way to inturrupt all channeled skill? Even if it's like a 2minute CD.

He is a hard thing to deal with in lane. His wave clearing ability is insanely strong right from the start and his meditate is ridiculously powerful. This two things make sure that the mid laner has really nothing to do against Yi. Shutting down Yi early is usually the responsibility of both the mid laner and jungler, since Yi is going to Alpha the wave it means it is going to be pushed up, so it is usually an easy gank.

"omg a turret and 3 champs are attaking me... lets press W to completely stop 2000 damage and then R and run away......."

like really..... u really disagree on his W nerf????? REALLY?????

Because Stuns, Knock up, Silence, Fear, Ignite and Grievous wounds don't exist

Because Champs without any of these debuffs don't exist..... there are like 30 champions that can´t do anything about this... thats the problem. also his W makes mid game laning completely unfair.

Does Kat not do pretty much the same thing?

Stop your whining. Yi instantly gains 300 MR and armor the moment you start the channel. You don't need the broken 4.0 AP ratio on it to use it well. It will still be very strong with a 2.0 AP ratio considering they buffed the base.

4.0 AP ratio was broken. It gave him way too much sustain during lane phase.

Let me go through your pros and cons list a bit more realistically:

Pros:
-Able to farm extremely well. - True
-Heal up full hp in seconds - True
-Does decent damage with Alpha strike - If by "decent" you mean decimating everything but tanks in one shot, then yes, decent would be the word to use here. However, I think the dictionary would beg to differ.


Cons:
-Extremely squishy and has low HP if you build him AP - True, but consider this in conjunction with his 300 MR/armor heal and the fact that he cannot be targeted during alpha strike, both of which abilities are refreshed if he kills an enemy.
-Easily shut down with almost any CC or ignite - Slows do not affect him during his ult, and any skillshot based CC is much more difficult to land during his ult due to his speed increase. Furthermore, CC's shut down everyone except Olaf during his ult, so this is almost a given for any champ and probably doesn't really belong in the discussion of any champ.
-Has only 2-3 useful abilities instead of 4 when playing AP - True
-He is generally only useful to clean up at end of fights - I assure you, that is not his only general use...But read the next point.
-He has to be fed to be effective - If you're correct about his proficiency in cleaning up after team fights, then he should be easily fed if the player realized his strengths. Which means he would then be useful in more than just cleaning up team fights since he's fed, getting him even more fed. Circular reasoning between these two points makes them into an actual PRO rather than a CON.
-Long cooldowns - Unless you kill someone with your ult. Then you can potentially alpha 3 times within 1-2 seconds; I've seen it done.
-Shut down in any decently experienced ranked game - Maybe
-Generally a pretty weak late game - I don't find this to be true, but I guess it depends on the team he's facing?

Your kidding? So your playing with a team with 0 ignites and 0 cc? Ouch.