Well enough armour can make you shrug off arrow shots. Plus keep at your suit of black armour, since armour heirlooms got a buff it seems. Shrugging off arrows is the main benefit.
Armour in melee is not that big a difference when fighting with armour killers (high cut or anything with pierce or blunt), but can make low damage weapons glance forcing your opponent to actually have to make his blows count.