I don't have any 'herd bound' or barn sour horses. When we train, we make it a point to always take separate rides, rejoin the group and separate them again as we ride. We do this at least once on every ride. When I get a green horse back to the barn, I always ride it away from the barn again, never stop and let it rest unless it is moving freely forward, and I make it a point to stop and dismount somewhere other than the tack room area. I never put a horse up until it has stood quietly for a while at it has been untacked.
If one rides and handles horses with the objective in mind that you want to prevent barn sour and horse sour problems, I have just found I never had any of these problems.
Some horses are more 'lonesome' and more 'herd dependent' than others. When we have a horse that is very herd dependent, it spends a lot of time tied out by itself until it figures out that there is life after separation -- I think they just finally quiet down when they figure out that they can be separated from their herd and they are going to be put back together later. It is like something just 'clicks'. They will just be tied up away from other horses and they just drop their head and rest a hind foot right away. At that point, they usually quit fussing over being separated. But, even with horses that are overly 'herd conscious', they are always very obedient and never fight with a rider and never try to go back to the barn or the herd.