Regarding Sivir nerfs
While i can understand Sivir is too strong in a competitive environment such as LCS/LCK/LPL (RIP i don't know SEA League), i don't think nerfing her is a good idea.
Why it is not a good idea? Because she is not terribly unfun to play with/against (cough Kalista cough), and while she has a really high winrate, the same can't be said for her play rate (cough Vayne every game cough).
Have you ever seen a QQ thread about Sivir? No you haven't, and there is a very good reason to that: she is healthy for the soloQ environment and for the game in general: if you lose to a Sivir you don't feel like a shit and you know you could have played it better.
Sivir is not Leblanc: if Leblanc is oppressive in competitive then sure as hell she needs to be nerfed else every single soloQ game will be plagued by her stupid no counterplay kit, while if Sivir is oppressive in competitive....no one really cares, she's ok and fair in soloQ.
I don't even play Sivir that much, and i have 0 problems facing her/playing with her in my random soloQ game. Pro players are just pro players: once Sivir is nerfed they will abuse something else.