Getting S grade on certain marksmen seems unreasonably hard
I've been playing Ezreal, and through all of last season and so far this season I haven't ever managed to get S grade with him. I went 9/1/6 in my last game with him while I had some feeder allies, and that got me B+. I feel like the whole 'don't feed the enemy thing' isn't appreciated enough in the grades, at least not for marksman champions in bottom position. I did a lot of damage to enemy champions, too. I just don't get why I can play to win and get punished for it.
Kind of the same reason in ARAM. I can play super tanky, get an insane win rate in ARAM by tanking really well game after game, and I end up with really crappy scores, sees and bees plenty of times. Usually when I get A or the super rare S(rare for ARAM at least), it's because I went carry.