[{quoted}](name=i8 GTX TITAN,realm=NA,application-id=LqLKtMpN,discussion-id=3oErKIJs,comment-id=,timestamp=2016-04-23T17:43:29.267+0000)
I think there's something wrong with your grading system, SERIOUSLY!
http://s31.postimg.org/9c3xas0jv/Ranking.png
As you can see, even Kalista, and Volibear have an overall better score than Nautilus (aka Fake Mr. Bubbles). Yet they didn't get an S Grade, but he did.
It's a lot less about score so much as what you did to help in the game, it's not a dumb system and that's what many people aren't realizing.
Damage to champions, turrets taken, damage to turrets, neutral objectives taken, wards placed/cleared, damage taken (good thing so tanks can get good grades for absorbing a lot of damage for their team), amount of time you cced an enemy, shielding/healing and I'm sure there's more that I'm missing.
Take into account all of these things because KDA is the least impactful factor that decides your grade.