[@The Harbinger of Ferocity][@Gordian Nought]
The mill is visible on the lower left corner of the map and given [@Norschtalen]'s description of the route, I do believe you are still on the opposite side, only being able to see the raiders thanks to the fact the raven is out there. So yes, arrows would not be a suitable weapon from your current position. As for the flanking thing, it would be difficult, very much so. The only way of doing that would be to sneak by them and since they are not exactly close to the mill except when tossing a torch, they might well spot you mid attempt.