Really the whole season was about why it's not a good idea to include self-absorbed newbees at swing parties...
Susan and Janet sure made a lot of nasty drama at Trina's parties... very hard to imagine Trina kept including them. (More like impossible to imagine.) One of them - Susan and/or Janet - caused a big scene at every single gathering.
Tom & Trina were great all the way through. Good comunication, treating each other with respect, love, forgiveness, understanding, patience. (They put each other first in every way.) Susan & Bruce and Janet & Roger were drama with a big D - we wouldn't go near such people.
In the end, swinging was only a sub-context for the show. The real focus was sexual & emotional exploration in general (first crush, first love, first swing experience, first cheating, etc.)