There is a new system in LoL, Champion Mastery. (not to be confused with Masteries)
It shows to a player his own performance compared to other players playing the same champion in the same role.
The score you get depends on some metrics, but they aren't discussed in detail:
It’s based on the champion and role that you just played in a game.
So, for example, we look at Annie mid differently to Annie support. We
take a series of performance metrics and compare how you do to all
other players in your region in your champion / position combination.
It is percentile driven – so earning a high score means you performed
in the top x% of players on that champ in that position. The grade
itself governs the point gains.
Question:
Is "top x% of players" determined by comparing performance of all players irrelevant of their ELO?
In other words, when a silver player scores S+ does that mean that he performed as well as a diamond player?
(If that is the case, my guess is that S+ in lower ELO should be rather rare excluding smurfs. Do you see this happening in low ELO?)
Or does a player get compared with roughly same ELO players when determining his score?
Best Answer
Yes, that is correct.
Champion Mastery takes into account the position you've played and compares your Score (Overall Parameters, not just K/D/A, however details are unknown) with the score of other players playing the same champion in the same role.
It is incorrect however assuming that:
This is incorrect as even if the Diamond player can only play that champion with a B- rating, and you succeeded with S+ rating, despite you having a better performance, it doesn't necessarly mean that you are better than him (since he is facing stronger opponents after all), it means you perform better at your ELO than he does at his.
Short Awnser, yes, it is independent of MMR