Finally beat it, after trying for a while. I found that in the final fight it's easiest to let the assassins come after a character that can survive their attacks, focus fire on each assassin until it's dead, kill the bishop afterwards and then kill Duriken using Zophia's Lewd Glance and Tevoran's Enrage as needed to lock him down. And heal his multiarea attacks using Oksana's Multiheal as often as you can.
Also, I don't see why everyone says that the Cloaked Woman fight is hard? I never had a problem with her. Her multitarget spell doesn't do too much damage, her status effect spells are easily fixed with items or Oksana's Purify, and she doesn't have too many health. The most annoying part in that battle usually is to chase her around the map while she teleports around after you beat her soldiers.
 "World's End Chapter 2"){kind=icon}
 "The Peacekeeper"){kind=icon}