No, what is important is a good story and faithfulness to the original material. Worrying about gender balance or ethnic balance or "power balance" sounds like that political correctness crap that is ruining this country.
It's all important. Complaints about "political correctness" are always red herrings.
Whether you call it a red herring or not, if filmmakers focus more on making sure there are equal amounts of men and women or people of various ethnicities in a story, rather than the story itself or faithfulness to the source text it is a problem in my opinion. I am glad Peter Jackson is staying fairly faithful to Tolkien's text for The Hobbit rather than making seven of the dwarves female in order to provide balance. I like what I have seen of the Avengers project so far and I trust Joss Whedon will not feel the need to go the Buffy or River route and make Black Widow smarter, wittier, and physically stronger than the other guys just to provide "balance".
It's a red herring because it's a false dichotomy - filmmakers don't do it instead
of making good movies, and casting non-whites or women in any role has never actually done damage in and of itself to a single film or tv show or play. When you scratch the surface of arguments against it, you always run quickly into nothing more substantial than reflexive narrow mindedness at best and often outright bigotry masquerading as demands for "faithfulness."
It's a fabricated issue - a problem that doesn't actually exist
outside of the context of a conversation in which it's being complained about. Most objections to "political correctness" are simply unwillingness to be required to treat people with courtesy and respect.
I mean, here the knock against the movie is that the director might give Scarlett Johannson a more entertaining, sharper character to play than a comic book writer assigned to a minor character decades ago? Quelle horreur
- but it won't cost the studio a single ticket sold to anyone other than a few politically-motivated head counters, easily made up by improving the movie for the vast majority who don't obsess about such things.