I was stuck in the "viking age" context, so the skirmishers I was talking about where scandinavian dark age/medevial.
Since the warriors of scandinavia where freeholders, and the population lived scattered, horses for transport on land where common, and where brought to war for transport.
In many cultures, the "light troops" are effectively those who can not aford to be heavy infantry. In Scandinavia, it was mandatory to own a shield, spear and hand weapon, so you skirmishing kit/bow would be in addition to this. People where not as locked in designated roles.

This relates to dual wielding in that there would be no reason for a viking age figther to deliberately go into action with a weapon in each hand. He HAS a shield and spear as well.
The only thing I could see happening would be holding a axe or javelin in the off hand for use as a parrying stick, if you have lost your shield for some reason.

Sorry to pop in so late. S

Some items.

What Gunnar was using is the atgeir -- no one is quite in agreement what this is, linguistically it is an "axe/spear" and I have seen this reproduced as a short hafted bill or "gisarme".

Two swords apparently are discussed in de la Torre's fencing work of 1474, we have this from Pacheco. It appears in Godinho, but more of a legacy weapon, treated in the same manner as the Montante - in a series of set plays. It is civilian, except the context is fighting against one or more opponents, sometimes multiple shieldmen,

Over and out.

Steve