Matchmaking ...

Hi, so I've been playing ranked duo since I started ranked after the promos in S4 but I had a win rate of ~65% hardly having any bad games or at least no trolls or leavers. But recently I decided that I should be taking matters into my own hands when I started going solo on all games in ranked queue. I've so far played 10 games and won only 2 of them. What is really shocking that I either got a premade trolls who simply decide to do so for "fun" in ranked (2 out of 8 defeats) and some games I had a team member or two that were afk early game and just reconnect very late into the game just before the other team ends it (4 out of 8 games). The last 2 games were very competitive and I really enjoyed them ... until the adc (two games in a row adc same guy) went head first into the enemy team's base for no reason. My win rate now is 53% and decreasing due to the awful system. Wasn't getting a premade considered an "advantage"? if so then the system is rather unfair. If there's a rule that says that any summoner below Gold division (I'm Silver 3 and was demoted from Silver 2) can't have a high win rate then I'd like to know more about that. I've read the ultra-long "Matchmaking Explained" by a Riot employee and found nothing to serve my case. Could use some explanation here, Thanks