Grading system cares too much about CS in ARAM/RGMs with duo's
CS is an extremely part and in the past hugely underestimated metric that leads to success. When you're top, mid, adc or jungle and you don't know why you suck, "CS" is often the answer. But that's on Summoner's Rift, where you have 1 farmer per lane. When you're in an ARAM, hexakill, urf, OFA, nemesis draft, ... and you're sitting with more than 1 person in lane, you shouldn't be graded as much based on your farm because you might be INTENTIONALLY not farming when your lane buddy scales better with gold.
http://matchhistory.euw.leagueoflegends.com/en/#match-details/EUW1/3323339829/36603236?tab=stats
Just had this ARAM game reminding me how harsh it can be. This Syndra in my team was playing as good as perfectly. Only 2 deaths, which were when she was OOM and had a lot of gold. She intentionally didn't wave clear all the time because not only do our 2 ADCs scale better with gold, they also need the creeps to LIFESTEAL on. She only cleared when she had to (adcs being down, their team pushing in, our team ready to siege). When their Super minion clashed into ours, she'd grab it and throw it back away so our wave would hit their turrets healthier. On top of this, she also dealt by far the most damage to enemy champions. All of this on a champion with a mere 44.35% winrate on ARAM in a high ELO ARAM game. She definitely deserved an S as far as I'm concerned... But wait. Her CS... OMG. Only 41 CS in a 21 minute game. Shame! If she can maintain such high damage to champs without dying and without farming all the gold, while protecting the ADCs so they can, I'd say that's a hell of a performance.
I know this is just one anecdote, but I've witnessed many hundreds of these in the past. I love ARAM and RGMs, but I feel like the system fails to recognize what is good performance in these modes that aren't all about farming. Of course, getting that CS is still important. But it's more of a team effort rather than an individual performance. Having everyone trying to get that CS results in more creeps being missed and more abilities/mana being wasted on creeps.
tl;dr The grading system is fine in SR but is poorly adapted to game modes where people share their lane with multiple champions that are 'supposed to' farm.