Mastery and Matchmaking

Mastery is a relative measure of skill with too many arbitrary factors. I think a Mirrored 1v1 after L5 (as an example) would better represent your Mastery because your %success in the mirror would show depth of understanding and mechanical skill against a player who has exactly the same potential of winning given you are using the same champion.

After the Mastery 5, you would have to break 60% to achieve M6, 70% for M7 and so on. At this point you would be playing against any combination of team compositions as you are banning and drafting per your team's involvement.

I understand my example isn't perfect. But I hope I got the idea across...