I'm not sure if it's me, but despite the fact I play other roles a lot more often, I get S in support a lot more often than any other role, maybe it's because I use every opportunity to get extra damage with starcall, or that I farm assists with wish unintentionally, but since chests are rewarded to S ranks, I think supports will be seriously rich.
Deep Terror Nami1 votesMastery scores are calculated by comparing your performance with other people in the same champion and role, so most likely the distribution of scores is consistent between roles. If you get lots of S's, you're probably just doing good.
TeCoolMage1 votesyeah but 'good' is relative, I have this terrible habit of flash starcall equinox for kills and still get an S.
I'm afraid that it might just be me spamming my damage and not thinking about it to the point I get 2x as much damage but below average heals.
Void Nargacuga1 votesMastery Chests
Earn locked Mastery Chests by performing well across a variety of champions or as part of a team. When you or someone in your premade party earns any S rank, you’ll acquire a chest. You can earn up to four chests each month, and each champion you play can earn you one chest per season.
You’ll see which champs you’re eligible for in champ select and on your champ details page.
To unlock your chests, you have a chance to randomly pick up a key each time you win any matchmade game and winning with friends results in finding more keys than going solo.
This might help explain it.
Drackolus1 votesAh, but one per champ per season, and there aren't too many support champions in general.
TeCoolMage1 votesOk true,
unless you start bringing Rammus and Vel bot lane, then the standard for support widens ;)
Void Nargacuga1 votesThe role of "Support" is already very wide. You got Tanky initiation supports like 
, Damage supports 
(might be others that I can't think of), & Utility supports 
. Its very wide ranging so if it could work out as something along these lines then it could very well could be played as a support.