Even by 1066, the swords were long and heavy in order to penetrate the armor of that time — also the impact could break limbs, rupture blood vessels, or knock an opponent cold, irrespective of the amount of armor.
Consider the Scottish Claymore:
The last known battle in which it is considered to have been used in a significant number was the Battle of Killiecrankie in 1689.[You gotta love that name for a battle]
It was somewhat smaller than other two-handed swords of the era. The average claymore ran about 140 cm (55 in) in overall length, with a 33 cm (13 in) grip, 107 cm (42 in) blade, and a weight of approximately 5.5 lb (2.5 kg).[citation needed]
Try swinging that all day.