I actually had somewhat of the same experience. I seeded into Silver, and had the intention of making at least Gold 3 or so (I know I'm not good enough to try for Platinum or higher yet. After two matches in Silver 4, all of a sudden a huge balance shifted. Not only was I being paired with lower Silver and Bronze players (and lots still in their promo, with no wins), but I was being placed against higher Gold players (presumably because of my MMR). While there were many games where we could have won, I was stuck with quite a few teammates who either didn't understand their roles or were just plain outclassed by their opponent. I don't think one player's MMR should offset the matches that much, to the point where you get stuck that hard. However, it was the end of the season so it was partially expected.
Anyway, changes are coming with season 4 to make this better if I recall right. So it's just a waiting game.