Currently quests tend to reward relatively low xp and trash items. Putting aside that I'd prefer quests were more interesting in general (I typically just spam enter as the NPCs hit me with like 10 boxes of text, then go do some kind of fetch quest), there are some severe flaws to the current system:
1) Quests tend to reward trash items.
These things just junk up my inventory, and further deflate the price of these items in the Markets as everyone tries to sell them. I've never liked LQs or quests giving you random crafted items, because it takes away from the ability of crafters to make money by selling them.
2) Quests tend to reward low amounts of xp.
Quests take time out of your day. I could make way more xp doing LQs, partying, or even just soloing normal mobs (that last one is key). So, why would I bother doing quests, or if could just run out and kill mobs to get faster xp?
Quests are limited. Mobs are not. LQs are semi-limited, in that you can only get so many at a time, but they are repeatable. Once any quest you might do that rewards xp has been completed, it's gone forever.
Long story short, I think quests should stop junking up your inventory with trash items, and they should have big xp rewards. I spent all day today doing quests on my 38 THM. After clearing pretty much every quest in the Black Shroud (or at least Gridania), including a number of Grand Company quests, I've yet to gain even a single level. I could have gained a multitude of levels via any other method in that same time frame. Yes, I realize a lot of those quests were for levels way under mine. That said, those quests for folks around level 10? Yeah, they give like 500 xp. I can get that in several whole seconds just killing mobs normally.
So, what was the point of doing the quests? I don't know. Please consider addressing this for 2.0. Considering the xp rewards for doing nearly anything else are huge, and unlimited, I don't think it's out of line to ask that quests, which are severely limited, give rewards commensurate to the time you spend on them. They should be easy, though time-consuming methods of getting a lot of xp.