Yi is perfectly fine like he is.
I'd strongly debate that. Following the nerfs last season both to him and to his itemization, he isn't doing well. His damage is low enough that he's unable to do his job effectively more often than not, and the nerf to highlander's reliability isn't helping that at all. On top of that, his design is fucked because he's more encouraged than ever to build very tanky because he doesn't synergize with any damage items except BoRK and bloodrazor. Being tanky to make up for not doing enough damage shouldn't be a primary goal of his build.
He's not good at any level of play. He's barely acceptable at low level play, actively bad at high level play, and as close to unpickable in master+ as any champion can get. That's not good.
My suggestion would be to buff Rageblade for melee champions. It's currently so bad on melee champions that it's a trap on every melee champion except maybe Xin. Buffing that to the point where Yi can use it would give another full-damage item to Yi, buffing him and moving him closer to his ideal design.