Fed hiring is a PITA. It takes forever with little consideration being given by HR to either the candidates nor the hiring office. Group interviews are about efficiency and often making sure there's more than one "type" there... Race, age, sex, etc. When I interview I always ask what their timeline is...when they will make a decision...often they will offer up how many folks are being interviewed. Was one person the hiring mgr or othrwise leader of the group you could reach out to?
Also, if a fed job, you can call the HR rep where you applied to figure out where they are in the preocess. Be nice, they might be the problem.
