A guild as large as GAF shouldn't have any issues getting 10 players together to play raids. One hour a night, two or three times a week, and you would immediately start making progress. I have a really hard time seeing the 10 player requirement as that much bigger an issue than the 5 player requirement present for other instances.
I've yet to hear about any real effort put forth to assemble groups or plan things out so people can attend. When we put together the dungeon events last year, we would have 20-25 people show up for two to three hours, every week. All it took was someone to say when and where. Everyone was really polite, and if we had extra people show up such that we were unable to fill an entire party, a dozen people would volunteer to let others participate in their place.
Name a time, find 10 people to fill a squad, go into the instance, and start killing things. People will figure out what they need to do to improve, either on their own or through suggestions from their squad-mates, and eventually bosses will start dying.