I realize you're joking, but I'm pretty sure if ancient vikings (and other smiths throughout the world) had access to propane forges, mass produced steel (not iron they had to smelt and then add carbon to make into steel themselves) and power hammers - they would have used them. As it was, they had apprentices to wield heavy sledges to do much of the drawing out.
It's the end result that matters most.
Now, if he was at a Viking times re-enactment camp for tourists, then sure... hand hammer away!
Having done some hours at the forge myself, I can tell you when you switch from a 3 lb hand hammer to a power hammer, it's amazingly relieving and time-saving.