Considering that silver weapons exist, is it not plausible that silver could be melted down and used to produce silver arrows or silver tipped arrows? This would allow ranged classes to be more viable against Chosen while most melee PCs likely have magic weapon cast upon them.
They don't have to be a common drop, they could drop sometimes with Dunwarren specific quests.
Apparently these exist. But I've never seen them ever, so maybe up their drop rate?