I agree that the dance-off doesn't really bring anything new to the table, but it's not like they all could prepare a second 'save-me' dance, is it ? But it is a bit risky giving one judge effectively two votes, especially if that judge is the cranky, vindictive type.
Also, the moment that Craig and Darcy don't agree Bruno's vote is completely irrelevant.
However, as soon as the bottom two are revealed it is often quite easy to work out who must have gotten the least amount of votes, so that could be a bit of a suspense killer.
I would agree that the best scenario would be to scrap the dance-off and simply announce who has come last, and maybe have the overall winner repeat their dance instead ?