Riot doesn't fix characters that are cheap. They are more focused on releasing new champions that are horribly overpowered and also taking the existing high cost champions and not nerfing them or adding to their overpoweredness. So what you need to do is argue that Yi should be a 1000rp purchase. Then when you get that raised Riot will focus on changing him around so they can continue to rob every sucker out there that needs an unfair advantage to win.
While that might be true, and I wouldn't object to him being more expensive (and all other champions. Why should some champions cost less when we're supposed to have a balanced set of champions? But that's a whole different issue.), that really isn't the issue here. Also, it's a whole different issue. Also, they recently changed Yi's "Meditate" ability, so your statement isn't all that accurate. Also, notice that they just did an ANNIE visual update.