Large classes are becoming more common and so this is an important topic. You said that you have some Chinese students, but you haven't mentioned what other cultures make up your class.
The video really hits home for me and it seems like the exact same thing happens in my classess. I've found with my culturally diverse classes that more direction in how to form the groups is always beneficial - team work designs that give each person a specified and active role can help. When learners know exactly what's expected of them, they tend to be more comfortable.
I've recently been much more prescriptive about how I establish learning sets membership (these are course-long study groups) and I've spent a good deal of time attempting to make each group is as diverse as possible. I use all of the knowledge I have about the students, plus some of my own presumptions and assumptions, to mix them up. It takes me more than an hour for 20 or so students, but it's an investment of time that has been very worthwhile.
For shorter activities I often ask learners to pair with someone they have never spoken to before (you saw me do that last week :-)), or I will group people using cross-overs where, say, 6 groups of 5 become 5 groups of 6. With pair work, everyone is participating. These kinds of activities can be done with a class of any size.
I hope this is helpful.
Viv (Plymouth, UK and sometimes BC, Canada)