Mercy Rule:
I feel like Mercy Rule doesn't activate often enough and it doesn't feel like it happens at a consistent point in games. I keep getting thrown into games that are practically over and have massive margins between the team scores. This doesn't add any enjoyment to the game, in fact, I dread going into matches that are ALWAYS losing by significant margins.
I was placed into a game where 4 people had quit and the score was 2900-100. The game should've mercy ruled when 4 people quit. Or at least, I feel like it should. Don't subject 4 new people to a game they can't control. Instead, if more than 50% of the team quits, why not just activate the Mercy Rule right then, start the matchmaking process over again and place people into a new match with full teams?
On top of this, If a game is at least 70% done, don't add new people to the game. Just leave the teams as they are. Putting people into games that are basically complete just isn't a great experience and there's no enjoyment in the game.