My party were at Levels 13 (Vaan), 12 (Basch), and 14 (Ashe). (Balthier and Fran were both at Level 13, but Basch felt better for what was going on in the story, you know?)

As for strategy, I took ample advantage of that security key you acquire in one of the cells. When used at the proper terminals (which are marked on your map), you'll get a sixty-second reprieve from the alert status. Rushing from terminal to terminal as best you can will significantly cut down on the time you spend wading through hordes of Imperials.

And as for the boss, there was nothing to it. I just wailed on him with physical attacks and used Potions/Cure/First Aid appropriately; it took some time, but he went down all right. I didn't have any Quickenings at the time, but supposedly one of them will off him in no time at all, so consider that as well.