I don't think they're under powered all that much. In comparison to the other factions, their units holds up well. Their sergeant is one of the strongest melee troops available, their crossbowmen are like marines. Their range is fantastic, and in a pinch can make excellent melee troops.
They don't seem to do so well on the map's autocalc though, and players often utilize a method of fighting that works best against the cavalry desperate Rhodok and Nords. Their bolts are still quite lethal though, especially when full damage is turned on.