No S For Janna

Hello all, so Im just writing this to rage a little at the rating system for the champions. So I have been stuck with having 2 lvl 7 tokens for Janna which I need 3 to make her into the level 7 I strive to be. However, the last one has been impossible to get. Ive gone plenty of games with decent kda, wards, sweepers, everything. Ive played Janna mid and went like 7/2/13 because i though maybe damage was a problem. And then the one that really really bothers me is I did everything I could in the game, completely on point. 3/2/30....and I got an S minus! I mean that has to be atleast an S. But anyways I was just wondering what other people's thought on this is because I feel robbed and take it very seriously.