To my knowledge you can't parse enspell dmg (unless they fixed it?) so it would be hard to get a concreted idea of how well you did in the party.
Concerning dual wielding joy/justice... I don't own a Justice Sword, so my opinion on it is completely speculation. But my hypothesis has always been that Joy with /war will out-damage it based on access to a better WS and Berserk. If you dual wield 2 swords you are limiting yourself to lolSavage Blade.
And if I had to estimate, I would say that the added dual wield trait from /WAR would probably match up to the bonus from dual wield, or at least come pretty close to it.
Granted this is all totally not parsed, so take it how you will.
