Mastery should take into account once you reach full build,
And at that point stop trying to count CS missed at that point against you. obviously if I'm full build, I'm goign to give the CS to a teammate who NEEDS the gold.
It's really annoying to see ADC's stealing farm from other champs who NEED gold just to get their "S".
i cant blame them really, they NEED to if they want to get the S, i just find this stupid that the game REQUIRES you do this for an S because all it does it HURT the team, if your trying to win, it is just a bad idea to take CS from players who need the gold after you have reached full build. let alone have the game REWARD YOU for it.
Make the system smart enough to know that once i played is full build they are GIVING the cs to other teammates who need the go;ld.. not "missing the cs"
I really do love the mastery system. But I feel small things like this can improve it drastically.