"anyone who really consider 3 shots groups"
I know several, each one a successful deer hunter who figures they're never going to shoot more than 2 shots at a time; so if a rifle will shoot 3 in a row accurately it's good to go. Even that's sort of an afterthought, their primary concern is the cold bore accuracy.
Otherwise I think the larger the group, the more useful the info. I shoot a lot of 5-shot groups with some of my .22 rifles because that's the mag size.