Diadem is a bit of a dilemma.

When you use the DF to join a Diadem group, or to fill out your pre-made, you are stuck with whomever you get.

Sure, using party finder could still net you one or more people who will afk (which is the worst offense possible) or gather (at least they're doing something).

Going with your free company (make sure to arrange a group to go with when you are on) seems to be the best way to go.

I applaud the developers for trying something different. Sadly, the only way for them to know how to tweak Diadem is to release it to us players. Sometimes we players will use a feature that developers created in a manner that they were not expecting. So all we can do is offer our feedback and (maybe) provide ways to tweak Diadem so that is enjoyable for many.

That being said, based upon the stories of other's experiences in the Diadem, I don't think that I am going to get the pegasus mount. And I really want it, too.