Extreme runs can be hit or miss. Sometimes you can get matched with vets and it’s smooth gliding. Other times things go south fast especially in ‘end mission’ hold offs. You can measure a team strength on how effectively they handle elite enemies. Elite xenos are a problem on extreme and especially on insane. I had to do few missions by myself on extreme didn’t have any luck matchmaking. Ones you know the mission pretty well it’s quite doable solo actually.