I remember, as a new user, the Epic quests were a disjointed mess-simply because I could pick up various quests from individual books simultaneously, and I had no idea to try to avoid doing that--a quest was a quest, so I picked it up--and lost the continuity of the story. The Epics, indeed, felt pretty much like any quests to my newbie mind.
I see a LOT of new users doing the same thing, and sometimes accidentally do it myself. Pick 'em up when they find 'em, do 'em all out of order, never really getting the full story properly.
Why not just force them to be done one at a time--start at Vol X, book 1, chapter 1--and NO other quests in that volume become available until you do the chapters in order. Book 2 opens only when book 1 is done. Etc. I don't have a problem with having the different VOLUMES do-able simultaneously, but only one chapter at a time in each, as a prerequisite to the next.
Seems to me it would make the Epic story lines much more likely to be followed as intended, and prevent people from having 4 or 5 (or more) open quests from the same Volume in their quest tracker, essentially obliterating the narrative.