This is the idea:
Archers and Thiefs have the same extreme skill today.
Those 2 classes looks very similar, an archer is like a thief without shield, invi, pepsi, ..... , and with some more damage. Both have same extreme skill too, so archers and thief usually PK using the same way.
Thiefs use knifes, so if they PK from short distance its logic to me ( Using their Ex Skill ) , but archers use bow, so i suggest to make a new extreme skill based on long distance weapons.
I suggest this new skill have the same atack power than the old one but concentrated on 1 arrow.
So archers will be able to fire from long distances and can take profits of distance items.
With this new skill, the double extreme bug will be hard to manipulate.
Actual extreme skill have 8 arrows with X power each, i suggest the new skill have an atack power of 4X to 8X , can miss too( with a low chance please) .
This way we can have a diference between archers and thiefs and take more profit from distance items ( remember that archers dont have leyends force items, all we have are distance items)