each time you do the Tortollan 'Beach Head' world quest in a unique location, it counts as different.
Here are some tips from looking around myself:
Also a 'blue' quest does NOT mean you have not done it-it merely indicates the rarity/difficulty level/reward quality of the quest. As another poster mentioned, there is an app you can install to track it, but you have to have done so before starting the achievement, which I'm guessing is relevant to very few people who have ended up on this page. Comment by maitriUnfortunately Blizzard doesn't seem to provide a way to know for sure which world quests you have and have not done, even though they must have this data saved for them to be able to track it.
