Finished a game earlier today, where our team won by a lot, but my personal player ranking (1 - 10) was lower than a Yuumi on the other team.
It's great that I could hover the ranks and see why - love this. It was because even though she was involved in 5 kills and I was involved in 15, her kill percentage was 50% when mine was around 30%. Because she was highest kill percentage in her team, she got a lot of "points" for it, which resulted in her getting a higher overall 1-10 placement than me.
It seems it would be fairer if the kill % was perhaps based on kill % of all kills in the game, rather than by team? I think you'd then get fairer 1-10 placements