If a support such as Janna that doesn't do damage had this ability, it would still be overpowered.

If Soraka could run up and stand in the middle of 2 enemy turrets while they shoot her and 2 people melee her at the same time and her HP bar goes up at light speed, yes, that would be horribly balanced as well.

If a support doing this is terrible balance, why let Master Yi do it?

If you are stupid enough to not save a single CC to stop his W, then he deserves to heal that much.

It isn't like it was an 8-seconds long channeling, making him immobile or something...

It takes away one ability slot which could be used as a damaging ability. He only does damage through his Q, and a little bit via his E. If he didn't have that heal, he would be completely useless.

ap yi is getting buffed

they should make his q as physical damage.

League of Legends isn't a 16th century, British military fight where people line up like bowling pins in mid, 5vs5, ready to stand and die. Many games, yes, even in ranked, can be won without a team fight ever occurring.

There's no such thing as "just have everyone on your team blow CC on him", because he could just backdoor by himself all day and use his ult to run away. Anyone that tries to stop him is either going to die due to his heal, or watch as he runs away using his ult then comes right back after you leave.

Due to the unbalanced heal ability, plus free escape ult, you're spending probably half or more of your teams resources to deal with 20% of their team's resources.

Stun him. It's really that simple. A bunch of champions have stuns. He heals? Stun and kill him. He runs? Stun and kill him. He wants to fight? Stun and kill him.

My post above debunks your "just stun him" nonsense. LoL isn't a "everyone on both teams mindlessly run to mid to 5vs5 and die" game.

You need ONE hard CC...ONE. It is your team's job to save one, whether it be as hard as an ultimate, or as soft as a silence, you need just a SINGLE one to stop him from healing, learn to coordinate team fights please.