This is the unique beauty of Elex and in general G1/2/3 Risen1/2/3 series. Animals/monsters and humans - they do not like each other and as soon as they see each other they start fighting. So humans try to kill animals/mosters and vice versa. Player can use this rule very often in Elex to gain money and solved quests.
For instance:
I can`t kill reavers close to Small camp and Goilat. They kill me all the time ;( So I use Troll and after fight ( very, very, very short fight ) I loot bodies.
btw. All humans and most monsters have range and close attack type so using bow to snipe them is not good idea.
I think in this case, the enemies simply spawn in front of all the farmers, so what's the point of the quest ?