Yeah, Riot's matchmaking algorithm is jacked, as many have observed. It's rather unfortunate. One thing I do is stop playing if it starts to put me on a loss streak, because good chance it will just give me jacked teams over and over and over, 10 or 20 times in a row, so I stop playing that mode for at least several hours in those cases. In those games it is not tilting that is making me lose, just to be clear, it is getting totally jacked teams that are practically impossible to win with over and over again (ex: Heimerdinger on my team who builds five Warmog's Armors for no apparent reason, Ashe on my team who does less than 10,000 damage to champions after a 40 minute ARAM game, Soraka that doesn't heal and says to their premade friends that Soraka is actually one of the best ADC in the game if you build her right, etc; and not one but at least 2-3 teammates like that in each game), and matched every time against teams where 4 or 5 of the players on the other team all have their shit together.
Since I started to stop playing a given game mode after a couple losses in which I was matched with poor teams, I haven't gotten into any more streaks that put me with teams like that over and over again. Touch wood. Generally, I come back and get matched with "average" sort of teams again.
I think the fact so many LoL players talk about tilting and needing to stop after a bad loss or two indicates that there is something broken in the matchmaking, because that is not normal. In chess, for example, or basketball, you do not suddenly become shite because you have lost a couple games, pretty much you continue to be able to perform at the same level, or very close to it, as normal. It's only in League of Legends where people feel like a loss streak of one or two games becomes self-perpetuating.