PSA: In RANKED, winning is more important than your champion mastery grade
In my last game, Anivia legitmately refused to group because "I need CS so I can get my S grade." When I asked whether she cared more about winning or her grade, she answered, "the grade".
Go play normals.
Even better, go write a guide on how to throw a 14k gold lead at 24 minutes all the way back to even at 38 minutes.
When you care more about boosting your cs and kda than actually winning, you stop winning.
In closing, to the people who spammed the boards a few months back with "winning affects your mastery score too much" threads -- y'know, I rather liked it that way.