This is a good line describing the Berserkers from a famous icelandic poet, ' His ( Odin 's) men rushed forwards without armour, were as mad as dogs or wolves, bit their shields, and were strong as bears or wild oxen, and killed people at a blow, but neither fire nor iron told upon them. If your going for a historically accurate look you should think about removing all if not most of the chainmail, there is some nice leather armor models available for the vikings that I think would suit this early period better.
