Before I mention this, note that I will be one of those people who goes to a contested zone and grinds out my levels anyway. However, on beta before getting buffed to 95 I did a good amount of the quest lines and I think I was getting less than 1% per quest. It may have been a tad bit more, but since the solo mobs out in the zone are giving .1% a kill, its more exp worthy to just zone grind than it is to actually do the quests.