One of the greatest advantages of sword + shield style is that shields are trained automatically, without any actions required by the player. This places such weapons as staves at a severe disadvantage - while their maximum parry bonus might not lose much to a shield, it only improves by them attacking - not by them defending. Staves are a traditional wizard weapon - and they are not known for engaging in melee too often.

It would be nice if all weapons and shields followed the same formula in this regard: if you would've been hit without the bonus/penalty of your weapon, you get a chance to get an increase in marks for that weapon. The chance doesn't have to be 100% for everything, especially if you are using two different weapons or a sword and board style.