Jame's and Joana's guides are both very multiboxer-friendly in my experience. How many of the collection quests you do is entirely up to you. If your group can easily run 5-man instances, that is usually more profitable and better XP. With my 4 priests, I didn't have the luxury of being able to run instances worth a damn when they were still high enough to be able to get good xp from them. With my locks, I bypassed a LOT of quests because instance runs were so much easier and better XP.