Even a katana cannot cut through an oak boarded shield with metal rim and boss. A Danish sea raiding party of 200 men in a shield wall would trample 200 samurai into the earth. Not to mention that even a stunted norseman would tower a good twelve inches over the average samurai.
One on one the samurai would stand a chance if he was skilled with the naginata or nodachi, or some other longer blade.
It would take an exceptional master of the katana to beat a sword Dane armed with heavy sheild and axe or blade. The swordmanship of european history is hardly recognised. A sword Dane trained to fight from birth just as a samurai and could easily double the strength of their Asian cousins. Eastern weapons and disciplines have a romantic notion about them today, and often seem more appealing to us visualy and spiritualy. Nothing about fighting with sharp metal is romantic or spiritual. Vikings own Samurai.