WHAT ARE THESE CHANGES ON PBE?

So Riot is buffing Xin Zhao and Nidalee. Two champions who at the moment are strong enough. I don't understand why they are nerfing mid laners so hard ie. Fizz, Ahri, Syndra, Zed, Kassadin...and then buffing champs who are by far stronger than said mid laners. They keep changing the jungle saying they want it to be "more diverse" but lets be honest, there are about four or five good junglers (Lee Sin, Vi, Jarvan...). I am not a fan of these changes and I know many others that feel the same.