I don't believe in conspiracy theories, but I think the only thing that wouldn't be manipulated would be the viewer vote - there are too many scandals around those for the show to risk it. Manipulation in shows like this can be in a lot more forms and a lot more subtle than just scores and dance off results. A classic one you often see is when a rubbish contestant is getting the sympathy vote and the show want them off, they can switch from slagging them, to giving them nice comments - the public loses the fear factor of desperately voting to save the person the judges have been abusing and out they go. The tactic works in reverse too - if someone's good, but vote is slumping, give them a battering to galvanise the fear in their fans and get the votes up. Have you noticed how Mark this year reminds everyone after every single dance that he hasn't danced before, how Tess repeats that "Marky No Moves" nickname every week? There's obviously a script being followed there to push his vote. And of course sometimes the celebs themselves can throw the game a bit if they want out.
Although I think there are a lot more motivations behind these things than just the tour. There are always going to be motivations to get BBC stars a decent way through the competition, but I bet there is also a double pressure because people on Casualty or Easties will have a heavy workload in the day job, and I bet there comes a point where the producers of those shows want their stars back full time. And Strictly won't want to piss Easties off, because they want to keep getting a star from the show for every series. Jake might have been the one to go this week because EastEnders need him back full time for some upcoming storylines. I don't think it's a coincidence that it's a 2Male, 2Female final. I don't think it's an accident when dance-offs go to Len having the deciding vote... It's all just a version of reality.