Performance Grading System doesn't take support champions into account; S awards feel arbitrary
I have had games where I went 12/6/24 and not get S rank, I've had games where I went 9/7/19 and get S rank. S rank doesn't appear to have a direct correlation with overall match performance. And I find getting S rank with a support champion is particularly difficult, as you apparently need an ungodly amount of kills or cs in order to get it. (Or the grading system was just in a good mood.) Kills and CS are not generally available to supports.
In the linked match, I went 3/0/8 as Leona support, and placed as many wards as the next top three opponents combined. This got me an A+, which is frustrating because I have seen far worse performances get an S.
Back when performance grades were just a "Good Job"award, this probably wouldn't matter. But now that performance grades are your main means of interacting with the new Hexcrafting mechanic, the fact that S grades are arbitrary and unlikely to be awarded to Supports is unfair and needs fixing.
TL;DR: S ranks are arbitrary and hard to get for supports, needs fixing.
Edit: KyroRane and Mysticman88 have clarified for me what an S rank takes. Apparently the top 5% of Leonas are doing better than 3/0/8 in a 20 min match? Damn.