In many cases I run a dungeon with some close friends only(like 3), especially when I only have only an hour or so to play for the evening. The Issue I have is that we are rewarded the same XP as a full 6 member party. Being a developer I cannot imagine that it would be very difficult to allocate +% bonuses for parties that may contain like 3 members. This would allow me to play more often and not have to spend most of the night acquiring a full party.
Let me know what you think?