Joe- I think that issue of the actors being separated plays into how you feel about Doyle's concept(s) in general. For this show in particular, the concept, as I recall was agreed upon at the time, was inmates (with the exception possibly of the attendants in Pirelli and Fogg) in an asylum acting out the story as narrated by Toby. Thus, the only 'real' actor who experienced the events WAS actually Toby. Johanna and Antony were inmates 'playing' those characters, so they were playing them as through their own veil of interpretation, disconnect and mental rehabilitation. There was little joyful connection, because it was all through a screen of acting and people that were haunted by their own mental illnesses.
But what connection there was, I think was quite profound in its own way. The moment of Johanna and Antoney dueting on cellos was quite amazing, in my opinion.
Again, that is one interpretation of the concept. As I recall, some people thought the whole thing was a nightmare by Toby, and thus the characters would not have been 'acting,' but actual dream representations.
And yes, I've seen a straight staging of the work, and while I will always enjoy the score, I do this Sweeney is most effective when the comedy is somewhat suppressed, and true fear is worked with.
"Are you sorry for civilization? I am sorry for it too." ~Coast of Utopia: Shipwreck