I had no troubles (lvl 20) Gambits set to cure people, and take out guards first.
About the Zwill Blade. In the subcontrol room there is a cut out hallway not shown on the minimap, there are 2 treasures there. One has an
Ancient Swordwhich has 35 attack power. The other is just gil. Get that first if you want an easier battle.
If all else fails just go kill the Guard people walking around.