If they limit it to one book a day, then it would take you 2-4 weeks to get one drop at 2-4 days a week. Not only that, but doing the prior raids will also give tomes so spending your raiding time going back would actually ease the burden on raiders. World first groups are clearing in less than 3 weeks, and Yoshida already said that was as they had expected. Right now we're time gated where we get our clears on Tuesday and spend the rest of our time banging our heads against a wall trying to get the next level with no other progression path.