Master Yi's Q and W doesn't feel cohensive to his theme.
Master Yi seems like he would be a very agile swordsman who would requires both good reactions and outplay potential. However, he seems to be lacking on one of them.
His Q, while it can dodge abilities, is somewhat limited to the fact you need minions, monsters, or enemy champions near you to properly become invulnerable to skill shots. Even then, becoming invulnerable for an engage mechanism is kind of bad in itself, because it lacks counterplay.
His W makes him heal, which while you can tie into his background a bit, just feels unfitting as an ability for a champion whose identity is supposed to be a swordsman who is defined as a late game monster.
The rest of his kit is fine, but those two abilities feel out of place. As an aside, if the Reds read this, is Yi currently on the radar?