The grading system needs tweaking for flex picks

I've been working on my mastery scores for various champions, and I like to play support. Now I've noticed something peculiar: for similar kda's in similar games, I get much better grades with Nami and Thresh than with Morgana. Now, it seems logical that when determining your grade, the system compares your result to all the other players who played the same champion. In the case of Morgana, who can also be played in roles other than support, this is unfair; of course you're going to contribute less damage to the team as support than as mid (to take an obvious example).

When the new champion select is fully rolled out, I would therefore think it only fair that the system should compare you only to the same champion in the same role.