i was doing http://l2wiki.com/terror_of_town quest with a tank on vanguard and i noticed when killing sel mahum groups, that if i kill them one by one i get elite id quest item every mob but if i used aoe skill to kill whole group at once i get only 1 quest item. is this a bug or another brilliant ncsoft feature? i noticed the same thing with http://l2wiki.com/assisting_the_golden_ram_army when killing groups of stakatos with archer using burst shot.
same happens with ketra quest. using a magnus to kill 15 mobs with 1 tidal wave > 1 qi. problably another brilliant feature made by some korean wiz, maybe to avoid some kind of exploit? or just for the hell of it.
to me it seems like a game engine limitation and not like a conscious decision. there is probably something like a seperate "process" or "thread" checking for quest items to be awarded. this process is obviously of a binary nature - when you kill a quest mob you get a "mob killed" flag somewhere (1). the next time the "process" or "thread" checks if you should get a quest item, it sees the (1), gives you a quest item and sets the value back to (0). it does not care how many mobs you killed with your aoe, it can only differentiate between "did kill a quest mob" and "didn't kill a quest mob" even if this check is being run every few milliseconds, when you kill mobs at the exact same time (with aoe) it can only result in one quest item.
i see you're practicing your trolling skills. anyway i tried it on na and it's the same so most likely not a bug. every mob type has ai script and part of the script deals with awarding quest items when it dies, like the chance of giving item, to which party member (which btw is another brilliant implementation of quests - give only 1 quest item to 1 player in group, not giving item to whole group or multiple quests involving same mob which gives 1 item for 1 quest at a time) so either that script runs only once when killing group of mobs at same time or there's a timer in the script which prevents giving items too fast. i'm guessing they made this awesome system to prevent awakened chars from easily doing 50+900 quests on their subs, kinda like how they dealt with the old wishing potion quest exploit. instead of actually fixing the problem they implemented this crappy 80% inventory/weight limit when trying to take quests. still though, if possible i'd like to get an answer about the quests from innova if they're even allowed to mess with ai files.
from my experience on poling, if you aoe on quest item mobs, every killing blow gives 1 quest item, regardless if you kill 1, 2, 5, 10, 25, xx mobs in that particlair blow/swing/skill. that is if the quest item drop rate is 100%.