>>299610408
>30 person instance where they all break into their own impenetrable groups
I find the groups in the 30-person instances to be the most penetrable. 
Or rather, there's the most opportunities, because you can just hop around many groups that are talking, looking for topics that you might be interested in. And the other people run around as well, every time someone leaves is an especially easy opportunity for you to sub in.
This more fluid structure I feel is also less stressfull, because the required commitment and participation is lower. More people can share the (from an awkward person's perspective) "burden of speaking", so more people are entertained more easily.

In a small group, someone shy has an easier time to show more of himself. To have a bigger share of the overall conversation also comes with more responsibility to interact, though.