Feast or famine players need to be punished for not fixing their play style
This 4v5 game that we won pretty much sums up the issue.
https://i.imgur.com/cz1P5KB.jpg
My team has two Diamond players: myself and Riven.
The enemy team has four Diamond players, but all four of them are feast-or-famine players, meaning that they're extremely ahead or extremely behind in 9/10 of their games, and never in the middle. In this game, we got slightly ahead early, and then they basically kept inting into us, because they had absolutely no decision making skill.
This really needs to be looked into. Learning to make good decisions and play strategically should be a requirement for climbing in ranked. Players who just go balls-to-the-wall 24/7 and hope they get far enough to turn their bad plays into wins via the numbers game should not be able to reach Diamond.
One possible fix would be to give LP penalties to players who have more deaths than kills + assists in more than 70% of their losses. This is a pretty clear indicator that they're not playing intelligently.