players with terrible scores should lose more points in ranked than players with better score
I think performance within the game should affect how many points you lose. If you have the best score on your team which is a combination of your KDA, ward score, dragon/baron captures/steals, turrets taken, gold earned and other metrics then you should lose less points than the person who has the worst score. It should be ordered from 1st to last 5th with the 1st person losing the least amount up to a cap limit and the 5th losing most.
Of course it should also be adjusted for the role you are playing. So if you are playing a support and mostly just have assists, and a mid has all the kills then that should be taken into account when calculating your score.
using R every time its off CD and all 5 enemys are up will have higher damage then the karthus who holds it to help in a fight or secure a kill.