I really like "Passing". In fact, I think it is one of the best "filler" episodes ever on B5. The motif of Gethsemane is used powerfully, Brad Dourif rules, and it doesn't bang you over the head quite as hard as JMS usually does.
I don't find the Kosh revelation at the end of S2 to be cheap or trivial...but, it IS somewhat derivative. Still, I like the idea of the Vorlons being so involved in our evolution. Particularly, when we learn the entire truth about them. It's very DUNE. But, JMS (and a lot of TV in general)...