normal MMR and solo queue MMR are different, its not always about lowering your MMR, i have had accounts in high diamond, getting matched in low bronze, because i have only played normal's with my lower ranked friends.. The problem from my experience is caused by if you play normal games with people of a certain elo, your normal MMR will be higher. For example if a bronze player is queueing with 4 diamonds, he will be matched vs higher elo's when solo in normal games, and if a diamond is queueing with 4 players from lower elo, when he goes solo for normal's, he will be vs lower elo players, there is not much that can be done to fix it. I know its not always fun to lose a game like this when its very one sided, but try to think of it as an opportunity to improve your gameplay, and learn from good plays they may do, their pathing, their positioning, etc.