One way to make any calculations fairer, is to take into account the size of the guild. A large guild can simply cull its underperforming members to boost it's GE percentage score, and the 'system' which selects opposing guilds for the International Guild Expeditions/Guild Championships equalises this by ensuring guilds are matched against other guilds of similar sizes.
I would like to propose a new metric, which I will call the GE factor. It is simply the percentage score a guild attains in GE multiplied by the no. of guild members. Example to follow...