Are they ever going to fix AP Master Yi....like he can attack the first minion in the line and still hit the champion and even if you do get on him without a stun or knock back or some sort he just heals right through the damage being done to him. The champion is an ad carry but we can build him AP and still kill everything. Im just confused on how this is right at all.

Magic.

So can Katarina's bouncing blade, just how his mechanic works.

He only has 2 abilities that directly benefit from AP and that is his alphastrike and meditate. His E and R don't benefit from AP AT ALL! Only reason AP yi is a considerable threat is if your teamfights are taking so long that he can throw multiple alphastrikes.

How to kill AP Yi:
1. He alphastrikes into the fight
2. Focus him (don't stun yet)
3. He starts meditating. CC him (pref stun)
4. Kill before stun wears off and he can ult and run off

Not really rocket science, although I'll admit his earlygame laning phase is OP as hell without your jungler ganking him right after an alpha strike.