It's actually a new feature. Riot has heard for a while now that Ranked is hard to get into and stressful, and they've finally answered! By having it so one team always has a toxic player, one no longer needs to worry about his own performance through the games. Doing poorly? No worries, your jungler already left the game after a failed gank. Doing well? No worries, one of your solo laners has decided to afk in fountain after a ks. And sometimes, the same thing happens to the enemy team! So at times you'll be getting stomped and still win (for free)!
As a way to nurture pride and accomplishment, each player can now focus on his own individual improvement. Because the rankings themselves sure as hell don't mean anything.