Finding players doing missions you specifically also want to do is currently super cumbersome. If the Active Recruiting flag was surfaced in the UI, I think this finding players to group with in game would be much easier. I made a couple poorly edited screenshots that show this.
UI shows there are groups looking for more members in the Advanced Quest category
UI shows groups actively recruiting for the top 3 missions
I didn't make one for the difficulty, but some indicator there would be great as well. With these adjustments any player could quickly find content to do with others, which is ideal for class experience, loot, and playerbase health.