That's just how it by design. There's no getting past that. I ran my casual 8 man premade for the last 6 weeks before it was yeeted. The only thing we had was a good defense. We stayed together. However, we had no shot caller, and we were very horrible with gathering kills. Despite this, if there was no other premade in our room our win rate was around 60% for that time period. Not close to the 70% - 90% that people have done, but close enough to where it could be called a problem. If there was another premade, however, the win rate drops to 0%, my only personal proof that it's impossible to balance games around premades. I wouldn't be surprised if half of your games you're with a casual premade that is just here for experience points. People do be doing that to enjoy time with each other instead of suffering solo q. However, it does be hard to tell with the lack of matchmaking. All you see is the dominating group. That's it.