Master yi changes. I have no idea how the W will work.

HP regen decreased to 1.5 from 1.5184. Alpha Strike (Q): Cost decreased to 70/75/80/85/90 from 70/80/90/100/110. Meditate (W): Cooldown decreased to 25 seconds from 35. Healing per second decreased to [20-80] from 30/50/70/90/110. No longer amplifies healing based on missing health. New effect: If full channel succeeds, next 3 attacks restore [30 - 50 (+20% bonus AD)] health and reduce the remaining cooldown of his other abilities by 1 second.

These are the changes. now lets go into the specifics of how this will change master yi. For yi jungle it does nothing but buff him and force him to go in or waste a pretty damned good buff to his autos. I have absolutely no idea if it will work however since he needs some form of cc removal and edge of night+cleanse arent avalible to him. Basically ask cowsep. But yi doesnt care about meditate in the jungle.

For yi top it becomes alot more intresting. Currently you can easily get kills and survive ganks simply by maxing meditate and waiting for the enemy to use cc. Worst case senario you get bullied under turret and meditate whenever your low removing the enemys ability to poke you. In a way you play exactly like irelia in the opposite manner. You go in alot to kill your opponent but unlike irelia you try to stay on capped health rather than lower health. Now heres the thing that makes or breaks the buff.

Since i feel context matters here i will explain how meditate works right now. Level 1 meditate is a health potion. Basically barely worth the mana. Level 2 meditate is significant and on the range of an ability that would have a 10 second cooldown. Level three it becomes a damned good ability worth leveling. At this point you break even on the powerlevel. But the reason you max it is due to level 4 and 5 becoming so absurdly strong. You can almost fully heal your health bar back from 100 hp. This is significant because it means you dont need to build lifesteal items like every other adc in the game does. But heres the problem. The healing from low health allows it to be a significant combat stat and gank avoiding stat. Which means you can easily end up surviveing massive ganks by simply meditateing and timing your exit correctly(remember cc has a cooldown).

How long does the auto attack buff last? Nerfing the heal so hard that it becomes relatively a gimp to have to use means the buffs have to last a significant amount of time. Certainly the 10 second removal will help but yi top doesnt max q first as such its going to be mana draining as hell. Which is why how long the duration is makes the differnce. If i can hold onto it until a darius puts the wave into turret i get the win. On the other hand if it goes away before that then i lose.

My point is if you nerf the ability into becoming a weak 4 second channel with a large upside if you finish it, the upside needs to be significant for enough time that it isnt a waste of your time to wait the 4 seconds. I honestly am not sure if the extra 50.46 health you will get in jungle or the extra 86.3 health you will get in top (trust me its the better one in this scenario.) Or 83 is worth it.

TLDR: i cant tell at this point whether the changes to w are buffs or hard nerfs.