regarding damage mitigated on others...

So I know riot mentioned that they are working on having this be displayed as a post game stat but is it currently tracked in game right now (and just not shown)?

I've mained kayle or ori for like 2.5 years now and they both rely heavily on shields as a large part of their support ability. I can go like 6/3/10 and get an S building damage or playing a damage support but when i go 1/0/22 or 2/0/28 or 2/0/17 I only get A or A+ even though my shields (most evident on kayle) completely turn the tide of multiple fights and allow a carry to snowball as a shield supp it really becomes evident that either the game isnt tracking ally mitigated damage or doesnt weight it high enough.

An example of why the game needs to weight shield supporting skills better:

I'll use kayle because her shield ability is more concentrated and easier to figure vs ori's. At least 8/10 ult uses saves a life when I'm playing kayle on average. 1/10 they die anyways and 1/10 they wouldnt have died had I not used it (likely due to my moderate heal). Some matches have long downtimes with few team figts and others are consistent skirmishes leading into teamfights. My ult has an average cdt of 50 seconds due to rushing cdr. Considering cdr and occurrence of instances where i can ult id say on average i ult once every 2 minutes. If matches are 30 minutes long on average, subtracting 9 minutes for lvl 6 gives me at least ~10 ults which means I prevented 8 kills with my ult alone. These 8 preventions should be worth at least as much as a kill. This would change my kdr drastically and is a significant part of why in the examples i mentioned above I should have gotten an S.

The calcs above are on average. The kdr's i mentioned in the 2nd paragraph are from games that are above average. Those matches tend to have significantly more teamfights which provide me more opportunity to ult. In matches such as those im ulting about once per minute (more often at the end, less closer to lvl 6). Assuming match time is the same this gives me 20 ults and 16 prevented deaths. Those deaths not to mention the associated prevented assists should give me an S even if i had died like 6 times vs the 0 deaths that I had. Some of you might wonder well there are other things supports need to do like vision score and cc score but keeping those the same and simply building damage with a kdr like 6/3/10 consistently gets me a higher mastery rating than 2/0/28 which is why this is a problem because it's evident that shielding damage isnt being considered as much as it should (or at all).

TLDR: riot needs to let the mastery system better account for shield and heal (to a lesser extent since healing is already tracked) supports.