It is very good NPC can fight each other. It brings more realism.
But it isn\'t good that you can\'t attack them, because you have to be grouped with one of them, which is nonsense.
It is like the rogue and tefusang were players.
Another thing is that this should never happen and players shouldn\'t be restricted to kill NPC only when grouped.
I understand this system stops unnecesarry complains, but it is done by hard. Like an invisible barrier which has no right to exist.