One of the problems with calculating afflictions from firing multiple arrows at a single province is the chance that the arrows will hit a survivor - where one arrow isn't guaranteed to kill a scout two are extremely likely to kill one. Killing power for two arrows fired against two scouts in one province is greater than the killing power of two arrows against scouts in two different provinces.
Those who survive (the afflicted) aren't likely to survive two, you regain hp when all arrows have been resolved. Though thinking about it, the effect would probably not be very significant on the results
From what I recall someone said that seeking arrows deal 8 AN Damage. That is: 8 damage + DRN - DRN per arrow.