Why is individual ranking based on team performance?
The whole concept of the ranked system is so that players can play with people of a similar skill level who will actually try to work together to win, unfortunately there still are trolls and rangers because that just some peoples personality. However when you as an individual lose ranked games die to these individuals or just a teammate who had really bad luck I fail to see why your rank goes down because of someone else' performance. Your rank should be bases on your individual performance as a player. For example if your team got stomped overall like 30-10 but you went 7-5 I fail to see how this shows that you aren't ready to play with people of higher rank. In fact this should BE the evidence to show you are ready, because you're able to maintain a positive KD ratio despite your team losing ! To prevent this system screwing the lower kill earning positions like tank or support just add their kill participation or assists.
Riot please make the individual rank based on the individual, not the team.
My 2cents