Creating a quest progress bar for each zones might attract players to further explore areas after main quest or known sub quests are done. Also a good motivation for perfectionists. Currently the only way to find whether there are quests in the area you're in is to search forum or expect random encounter while you explore. Well, random encounter sounds like an ideal way to 'adventure', but little tweak to make one's life easier is never too bad, imo. You can add achievement mark on each zone's overview map so players can acknowledge if you've completely explored the area. If new quest are added in future release? Completion mark will disappear from overview map can player will wonder, and go to the area to seek out added quest. Which makes reason for players to come back to previous zones. What do you think?