In a game with a good sense of community, you will very rarely ever group with anyone you don't regularly group with, and dislike it when you do.
This is disturbing to me. It seems that these people don't want to group with anyone outside of their guild but don't want anyone else grouping either.
Is this some form of guild blocking where you are trying to make the gear in instances more exclusive?
Community in an mmo is the interaction you have with people outside of your clique. Everquest had a much better community than modern instanced games and i loved grouping with new people.