During the last month I noticed a change in quality regarding matchmaking. At first I thinked was because of a golden week or something, but then something made me think about a different cause (I strongly believe that during week end/holydays MM can't handle the casual players).
I had a constant good winrate, and at some point dropped to almost 50% . Every game was like head or tail, you had an afker or a troll, or enemy team had.
Long story short, some days ago I had a message in game, asking me if I enjoyed LOL in this period.
After this, game looks more normal to me.
Did RIOT tested a new MM system?