Does upgrading the vault door do anything other than simply slow down (and not by much in my experience) the raiders trying to get into your vault?
I mean I appreciate the delay so the armored and gunned up people can get to the entry way to stop them, but it just seems like that is all it is good for, a bit of time before they will always get in... with their swords.. some how getting through 5-6 feet of steel... Whatever.