Matchmaking: Explain me this please

After having my last 20 ranked go down from like 70% to 40% I get a little winstreak win 6 games out of 8, and bring the win rate back up to 60%. Then watch this, the win rates of the last 20 ranked played from my team and the enemy team:

My team: ----------------------------------- Enemy team: Top: Sion (me) 55% --------------- Lucian 75% Jungle: Shaco 32% ------------------Vi 60% Mid: Akali 60% ------------------------- Katarina 68% ADC: Draven 55% ---------------------Kog'Maw 70% Support: Nami 67% ----------------- Leona 90%

Total: 269% (avg. 53.8%)-------- 363% (avg. 72.6%)

By the way the Support and ADC on the enemy team are duo and obviously smurfing. Also, after looking through the games I started winning after my loss streak, my teammates had higher win rates then the enemy as well.

I will create a spreadsheet of this and post another thread when I got a few games for more concrete statistics. I swear matchmaking is rigged though to keep you at 50% win rate. Thoughts?