The big thing on meditate is the 300 armor and magic resist he gets while using it. Anyone with silence or stun get's rid of all of that. Do not even attempt to burst him down while he is meditating, you will just waste your spells. Either stun him, or let him finish and mess him up. Even if he heals back to full, you will do way better if you wait for him to end his channel, because those bonus stats make him damn near invincible.

Next thing you know you're gonna say ap nunu is op, he has one AP ability, that one ap ability is suppose to be the equivalent of a full combo from another AP, or not even, it's just one Ryze Q lol.
and pick a cc champ if u get Master yi mid.

Play malzahar.

Mouse over enemy minions and press E.

Stay away from your own minions, especially when there are only 3.

Push push push push push push push so yi can't roam

If he alphas you post 6, just full combo him and kill him before he can alpha again.

If he tries to meditate through the damage just silence his *****ass.

GG AP Yi.

Have yet to meet a Yi that doesnt fall off after the 30 minute mark.

Still waiting....

Not sure how to nerfed that AP Yi; but the last game I play as Xin Zhao, my friends stop him with Lux's Light Binding, Hecarim's Onslaught of Shadows, and me, Xin Zhao's Audacious Charge ---> Three Talon Strike ---> Crescent Sweep to stop AP Yi.

just counterpick him with someone that has strong sustain and a stun/silence/knockup...i like cho personally

As someone who used to play ap yi i'll tell you he's not hard to counter. All you have to do is try and avoid getting hit by alpha strike (bing hit by 1 or 2 isn't the end of the world just avoid constant harass) and when he starts meditating (assuming you can't interrupt him) use the opportunity to get in the perfect position to screw his day up.