You dont have to join the order which has ur classes first skill. Some1 else can get it for u, or u can put ur alt in that order and get it.
Also, it seems that the skills which require 3500 prestige are tradeable on this server, which means u can just put 3 diff toons in the 3 orders and within bout 5-10 days of dailies u can get the 3 books for ur main toon.