Let Them Play Normals
Riot needs to start punishing people who are found to be intentionally ruining games by forcing them to play normals. For obvious reasons - feeders/afks/trolls get off on ruining lives. The goal is to improve ranked by eliminating 6v4s. Beyond this a nice side effect might be that people figure out Normals aren't that bad.
When you're someone who works a 10 hour day, and you get home to unwind, and some rager is throwing because, whatever, they've got another 6 hours of play time after the three they've already had, you're interest in the game is damaged. Moreover, when it appears nothing is being done about it, you wonder why you keep blowing money on skins.
These issues are hard to determine, so I'm not suggesting you break out the ban hammer, but something needs to be done, and removing them from the portion of the game with the post consequences seems smartest. AFKs always suck. But at least in normals you leave them after the game ends. In Ranked, we have to carry that AFK with us until we gain two more net-wins. Like everything else, the goal isn't to eliminate trolls - you're not going to. But you're aiming to decrease their influence to the point that it isn't determental to the overall scope of the community.
Last night I had two trolls in one game and I just ended up downloading HotS again. I actually think LoL is a much better game, but Blizzard at least makes the choice to have elaborate account systems in which getting banned has larger consequences. And frankly, as much as I have an issue with, I feel like they're doing something.
As FDR once said "Above all else, do something." I need to feel like you care Riot. And I don't.