S rating on Supports (In this case, Bard)

Right, I never really go on a forum to rant about stuff, but I saw it neccesary this time. I've litteraly had terrific bard games the last 2 days. All these games went terrific, landing double stun after double stun, clearing a lot of wards, securing most dragons, warding at key locations and in some of the games, decent kill participation. In two of the games my ADC even managed to get legendary due to a great laning phase (This is not solely to my credit, since I'm only one out of 4 players). Yet, in all these games, my grades have been nothing else but B+ and one of them got me an A. So my conclusion is this, either everyone in my region is serious pro bard players, or the grading system is working in mysterious ways that are ilogical. Honestly, I don't know how much better the game expects me to do, especially considered you're meant to play equally against your opponent since your MMR is about the same. Sorry for that rant, but I found it neccesary, as the grading system seems completely broken, and I don't know how I'm supposed to achieve mastery rating 6 and/or 7 at this point. Suggestions are always welcome!
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