Very sad news indeed, just read it elsewhere and was about to post it.
Goes to show that it's not always so glamour behind the scenes, movies are made by people devoting countless hours trying to make something they hope we'll enjoy, sometimes at the detriment of everything else.
That's the main reason you never saw nor never will see me trash a movie. If I didn't enjoy it, I'll say so but that's it. Very few movies set out to be bad, and the cast and crew worked just as hard as for any other movies. And to work on set, you need to be driven by something, the love of movies for most, it's not a job for everyone. That alone deserves some measure of respect.
Very interesting though to see Joss Whedon overseeing the finishing of the movie. I don't think it will change anything to Zack's vision, it's already far into post-production, but if you told me 5 years ago that Whedon will be involved in both the Avengers, and Justice League, I wouldn't have believed you !