Don't be mistaken. These men are not the fragile rangers that are common in the Ravenstern Kingdom. Their close combat skills are almost on par with their Huscarl cousins. Their shields may be weaker than those of the Huscarls' but they are definitely one of the toughest the major kingdoms can supply their troops. While the Fierdsvain's axes are the feared weapons of many soldiers, their short bows are considered a joke amongst the archers of other kingdoms. They have difficulty putting down top-tier infantry at range and are completely helpless against charging cavalry. They can barely function as skirmishers, due to their slower speed from the heavy armor they don. They will become the slaughtering machines like the berserkers and huscarls when placed in melee combat, albeit to a smaller extent. They fare poorly as ranged units, which can hurt them in a siege, as the range and damage of their bows cannot match the powerful longbows and warbows.
Note that while they play the role of archers, they can defend themself as well as any other top tier infantry and can be used as backup infantry. Think of them like legionnaires but with better range but significantly weaker stopping power.
They upgrade from their much less armored cousin, the Fierdsvain Archers. They cannot be upgraded any further.