Cant Get an S for the life of me, how does it work?

Before this patch I got S's every now and then, I had way worse games than the ones below and still got an S. For the ones posted, I dealt the most damage, had OK cs, and in a way carried the game, I don't mean to say that I deserved the S but why did my team mates get one and I didn't? Anyone have some thoughts? I watched Redmercy's theory (linked above) on it and It sounds pretty decent, the games below would support why support Azir got an S+.

http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2192086464/208618335?tab=overview

• Carried pretty well as Yas 18/5, got an A- but Support Azir 8/6 got an S+

http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2200134935/208618335?tab=overview

• Ez 10/3 Dealt almost twice as much dmg as the next person A+, while Shyv, Sona and Naut all got S's...

http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2198480954/208618335?tab=overview

• 15/8 Draven carried pretty hard A+, Diana 9/2 S+ (She janitor-ed a quadra, I dealt twice as much dmg)

http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2193015429/208618335?tab=overview 23/11 Lucian, the only game Ive gotten an S on thus far since the new mastery levels..

I feel like if they got an S or S's for their contribution, stat wise I exceeded them almost every time, thus I think I should've gotten an S? I wish I knew what the criteria was because this doesn't feel very balanced. I'm not crazy am I?