It's been debated for a while trying to incorporate Dual Wield as an option for GLA/PLD to increase their DPS if it weren't for the fact most of their abilities relied solely on having a shield equipped. I dunno how it would work for MRD/WAR however, though if the opportunity for them to use 1h Axes comes around they might even be able to utilize shields offhanded too to increase their defensive capabilities if a situation calls for it.