Just because the fact that he gets 7/8 and 9, doesn´t mean that he is better then a 2* or 3* that gets 5 or 6. I belive that a 1* player with a rate of 7 or 8 is quite "equal" to an 2* or 3* player that gets 5 or 6, since his performance is "outstanding" for his lvl but "okey" at a higher one. This is probably also why a player loses a * if his team advances or not. It has to be "linked" with the */q somehow.
I tend to count how many times a player gets mentioned due a game and then try to base a grade/measurement, do not relay on the rate