They have their own queue. The thing is, you’re just not restricted to only join competitive, rewarding BGs as a team. You are allowed to queue by yourself as well.
It’s hard to say why people queue solo, complain (regardless of how many different servers are represented on the other team) that it’s a premade, and it’s impossible to win, and call for their teams to just give up now.
If anyone actually thinks that it’s impossible for a PuG to beat a premade, go make a premade, and see how well you do.
Unsure how to start your own premade group? Well, here’s a little guide that I hope is helpful:
Good luck out there!
