1. World War Z
OK, we're not expecting Thor: The Dark World to be a masterpiece like the three films already mentioned, and all respect to Alan Taylor he's not a Spielberg, Coppola or Donner so perhaps for a better comparison we should take a look at a film more on its level, and more recent: World War Z. Released to mixed reviews -personally I had a great time with it- World War Z seemed destined to fail. Spending years in development hell before finally being picked up, the film went through notorious re-writes and re-shoots; the original script from Michael Straczynsk which stuck close to the novel the film was being adapted from was re-worked in to blockbuster territory by, Matthew Michael Carnahan. However after filming was completed there were not many happy with the final product, with director Marc Forster's direction of the film being highlighted as an issue as well a weak ending; enter Damon Lindelof. Lindelof was brought on to the project to re-write the ending, which was shot over a seven week re-shoot period. The ending underwent a major change, and you'll note that Matthew Fox (LOST) had only one line early on in the finished film which was due to his part in the final third being completely cut due to the re-writes. World War Z may not be a masterpiece, but it was a fun, entertaining movie, and the re-shot ending worked extremely well. These are just a few films that had to undergo reshoots to save the day or simply re-work then, and so there is then, no reason that Thor: The Dark World will end up a disaster. Re-shoots in films, especially blockbusters, happen all the time, and whilst there are plenty of examples of when re-shoots have spelled disaster there's plenty of cases where they weren't. And if the Thor re-shoots simply mean that we're getting more Loki, what's there to complain about?