I would love a generic repeatable exp mastery track in PvE that you can use without burning mastery points, similar to the reward tracks in PvP and WvW. I just recently learned about the hidden exp bar that is supposedly banking spirit shards until I unlock all the mastery points in an area, but it is still frustrating to feel like you are getting no progress when your exp bar is full and you need more mastery points. Heck, at this point I would settle for just making that invisible exp bar visible, tho I would certainly prefer selectable reward tracks.