... I'm pissed AF. So the other day, I played a match of kha'zix mid and went 24/4/10 (and this happens oftenly) and a couple of months ago 18/1/2 (Idk what's the exact number of assists but it's something similar) and I got A+ or A. I've never gotten S on kha'zix somehow. 24/4/10 and no S? BS PLS.
Rito pls. 
KoggyStyle1 votesIts more than just KDA and it compares you to others who do the same champ/role
GULAG 4 U1 votesI know, but honestly, Diamond 1 kha'zix has mastery 7 and I can't see that he went on massive KDAs in his match histories (He's in challenjour though).
Honestly, I've played with a couple of kha'zixes in the past and they generally fail.
EMeta1 votesKDA has little part of mastery. KDA, per time in match--weighted for how close in level your kill victims were--is what matters. But even that is only part of mastery. CS is a huge part, as well as wards placed and wards destroyed. Then the system takes that and compares you to the other Kha players around your elo who played well, and you have to be in the top 5%(ish) of them. Typically when Kha does well, he does very well, so there's a huge % of kha games where his k/d is above 5.
GULAG 4 U1 votesSo I guess I have to blame my shi**y cs'ing skills lol.
CerealBoxOfDoom1 votesCerealBoxOfDoom1 votes... I'm pissed AF. So the other day, I played a match of kha'zix mid and went 24/4/10 (and this happens oftenly) and a couple of months ago 18/1/2 (Idk what's the exact number of assists but it's something similar) and I got A+ or A. I've never gotten S on kha'zix somehow. 24/4/10 and no S? BS PLS.
Rito pls.
The Last Ballad1 votesAnd HOW is this related to the champ mastery lvl's? The grading system is what you are complaining about, so why do you think the mastery lvl's are busted? If you cannot play at the top ~20% of Kha'zixes, why should you get S's on him?
GULAG 4 U1 votesI'm pretty sure 24/4/10 on kha'zix isn't really a 'normal' kda you know.
It's not like it's possible to get 40/0/0 unless the enemy team has 5 int feeders.