Re: MCU Phase 3: Have it your way
In this case our investment is irrelevant. Whedon had to juggle four iconic superheroes and Black Widow, guy #6 is the one who would have gotten the short end, regardless of who it was.
The Thor scene appears exactly as written (the script leaked online a few months before they started shooting)
Team superhero movies should be about the team. Avengers was. Not every team member is on equal footing. There are leading characters and there are supporting characters. There are characters that drive a narrative forward and there are those who fill in the gaps, whether a film is about a singular character or a "team".
Where the X-Men films got it wrong was with the leading characters - Cyclops and Storm have no relevance to the overall structure of the films. Take them out and they're the same movies. It's Wolverine and occasionally Jean and the Prof versus Magneto. Marvel's merry band of mutants wasn't much of a band.
I don't think anyone's complaining that Iceman or Nightcrawler were supporting characters in those movies. At least, I hope not.