So far in High Isle I have come across two quests that were bugged and required abandoning/restarting to complete the quests.
The two quests were Ember's initial quest when trying to turn the guar back into a human and Escape From Amenos when trying to meet with the queen (she wasn't there).
Each time I submitted a /bug and was told to abandon the quest and restart. Since I was near the end of these quests, restarting from the very beginning of each quest was not fun. I would much rather break quests up into multiple sub-quests for each major action you perform than having to restart from the very beginning of these quests.