Final boss crit two handed power attack charge instantly killed a player on low tier. He also rolled a crit while I was playing, and failed to confirm. Fake Samurai Oracles hit damn hard apparently. The real threat is the ninja alchemists. They can really melt partys, especially if the party gets trapped in one of the smaller rooms or staircase by the front door.
Good tactics, cinematic battles, smart preparation paying off for pc's, seige weapons, this scenario has it all. It can be difficult to prepare for, don't try to cold run it, but the payout is quite nice.