If ya go through solo rank, that's the fate ya have to face with.
Unless, ya can force players to join ya at the same time with all mythic, or do some experiments with Unity engine to make better matchmaking simulation and suggest better mathematical formula to developers. umu. (If ya capable of doing that, better just make own game and become rich. Ahaha xD)
From my experience, there are 2 possible reason for these to happen.
1st..lack of players in the near Mythic 1 during your q. This rarely happen nowadays since there are more players in mythic 1 or 2 compared to last month.
2nd..which is the most likely possibility..the legend players are premade with mythic 1 players. And the matchmaking is set to follow the mythic level. Yeah..if this happen..sucks to be solo q players