Getting slightly irritated by a certain type of quest Bug. Namely, quests with a placeholder.
Experienced it numerous times when doing these quests that some random player not doing the quest (not of any fault of their own) kills the quest placeholder, resulting in me being unable to complete the quest.
The only viable option then is to log out and in again. What a bother! Even if it works...which sometimes does not!
Okay...muttering without providing a solution is pointless.
1) do away with placeholder quests...maybe not an option.
2) instance these quests....my preferred option.
3) If placeholder NPC is killed by someone not having the quest...all those with the quest are automatically updated. The quest is deemed to be completed.
Okay..this is my two-cents rant.
the game is mostly playable

Have fun.