Why is MMR hidden? Why don't you make matches based on rank?
Having an accurate skill rating for players is important, and players should receive the rank their skill level represents. I do not understand why you separate how you match players from their solo queue rating. It's frustrating and unintuitive when you match players with high win rates with players of much higher ratings because their MMR is high... If I'm a Silver 1 with a master tier MMR I should be playing with and against other Silver 1s so that I can climb quicker and arrive at the rating I am supposed to be at sooner rather than later.
Take a look at this scripter Xerath's matches: https://na.op.gg/summoner/userName=pentadunk dude has a ridiculous win rate, and if you look at the ranks he's playing against, he's being matched up with and against people 3-5 ranks above him consistently. Why does this happen? I feel like you're forcing a 50% win rate and forcing players to grind out more games than they should have to.