First of all, as a WAR, you really should be using a great axe or an axe. The skill cap is much higher, which means more accuracy and more attack (each skill point is roughly one point of both accuracy and attack).

Second, as a PLD, you shouldn't be using a great sword in exp. parties. Ever. PLD will always tank with the sword and shield combination. Losing such a valuable asset as a shield for slightly more damage (which isn't what the PLD's purpose is anyway), is a bad option. Giving up the chance that your shield will significantly reduce the damage you take on any given hit is just dumb. Aside from that, PLD's shield mastery would go to waste. Great sword isn't worth it in most situations, and by the time you can really put it to use, you'll be able to skill it up on your own and in skill up parties anyway.