I've never read Red Rain, but based on this one-shot it seems like a pretty generic Batman as a vampire Elseworld. As a chapter in the search for Palmer it means nothing (nothing different than the first two). As an Exiles issue it's okay, but you have to ignore the fact that the 'Challengers' say "I hope we were right not to get involved" at the end even though they totally got involved and royally screwed this world's Dick Grayson.