Hello,
I play using the French version of the rules.
It states for Arbon that he fights as if using a bow (it does not say as an archer).
Then the bow rules state that a character with a bow may use all his dice if fighting on the same space as a monster, but this does not apply for the archer.
The question is then: does Arbon merely use an arc, or is he an archer? The later meaning that he always must roll his dice successively; the former is clearly more advantageous.