I've noticed that the number of dropping quest items is decreased in several quests even in party.
For examples:
Quest guardians of the holy grail before 2-3 weeks after killing a mob 10 quest items(Monk's Scripture) had dropped now only 2 quest items(Monk's Scripture) has dropping.
Quest war with Varka before 2-3 weeks after killing a mob 10 quest items(Varka's Mane) had dropped now only 5 quest items(Varka's Mane) has dropping.
