I have always wanted a quest list for each of my characters, its hard to remember which ones you have done (especially when you have more than a dozen!).....but outside of the hero's handbook in gwen, which doesnt have half of the quests, there is no way to find out which ones you have done or not without going to each quest giver and seeing if they will give you a quest.
Prophecies was easier to remember which ones I had done and factions just didnt have all that many quests in my view. But nightfall has quests that you wont find unless you do A then talk with B and complete area C.....so I have missed a bunch with my characters there

. ah oh well.
Here is hoping its something they consider for the next gw.