also.... if you fail a mission, shouldn't you redo the mission?
I guess the campaign doesn't work like that exactly....
No, because that creates frustration. By default, you will replay mission you fail, but that's only if you're trying to play it straight through in "proper" order. YOu can easily skil around though if you choose. Like Rahdo said:
"If you fail your mission, you’ll try it again, no matter if you’re playing single player, co-op, or competitive multiplayer. We’re not going to force anyone to play all the missions in order, though. Brink is like a book… when you buy it, we’re not going to try to stop you from turning to the last page and seeing how the story ends. We’ll present it to you in the proper order, but if you want to skip a chapter, or play in any order you like, go right ahead. "