Parry is affected by STR but its like +1% parry for every 40 STR. YET without fending accessories you parry less often. So its stronger parry vs more parry.
Ideal would be Full Vit build (base+ gear +accessories) for harder fights and MIX of Vit (base) and Str (accessories) for easier content. Im running it like this, loosen VIT to 500 and up STR +40 and really...i don't see much difference