mastery calculation not fair?

I feel like the way your match performance is calculated for mastery points is unfairly rigged towards KDA happy carries. I play a lot of tanks and support champions and I've found it unreasonably hard to even an s- for the sake of mastery advancement past 5. From what I've been able to observe from my experiences at least, the mastery points are strongly weighted towards kills over all else.That skews things pretty unfairly for a lot of champions, especially tanks and supports who typically have few to no kills. As of right now I've been trying to grind out mastery for Nautilus, and I only need one more S to get mastery 6. Here are some scores from some of my recent matches (2/3/32) (3/0/18) (7/1/18) not a single one of those got me even an S-. it's gotten to the point where if I'm playing a tank or support i feel like if I have even one death I've already failed my chance at S and even if I haven't died even once in a match I feel forced to take unnecessary risk to to try and get kills even if it puts my team in a bad spot because as you see above I can win a match without a single death and end with 80% kill participation and not receive shit for it. I know in the next patch riot is tuning mastery for support roles but that still leaves tanks mostly fucked, and it also doesn't account for those who play support or tank type roles in featured gamemodes. I feel like more comprehensive adjustments to mastery score calculations are needed, thoughts?