Hmm, sometimes when I solo queue I get a premade duo as teammates and those matches aren't always sweaty. I think there's always a chance for a mix of premade with solo queue and that's because waiting for a new match needs to be reasonably short.
Anyway, queue numbers and time of playing are very important in determining what the lobbies are gonna be like. There's no way that the matchmaking selects certain players in particular and sends them into specific hardcore matches as punishment for their good plays. It's just a simple sort based on some stats and then players 1-60 on the list go to one match, 61-120 to the second and so on. If you're getting preds and masters in your lobby, congratulations! you're among the top players in the queue, way above the local average.
The problem is not with how the matchmaker works, it's the way skill is distributed. A graph of the skill from low to high level of play would show an exponential growth, with the skill gap between average and bottom player being being much smaller than the one between average and the top. Respawn can't do anything here, it would be unfair to keep high level players wait dozens of minutes more than casuals, only to have a sweaty match.