The episode ended in a very cliched fasion (it was their willingness to die for people that made them worthy, which is the reason 95% of people in Sci Fi seemed to be deemed worthy in situations like this), like I had guessed it was.
It wasn't just their their willingness to die for each other. It was their willingness to die "in the dark." Anyone can throw their life away for fame and glory. The Vorlons don't want glory hounds, it's as simple as that.