Apparently the final boss on normal difficulty is either Geralt, Amy, Cassandra, Hilde, Setsuka or Hwang.
Not gonna lie, it baffles me. Not even Nightmare or Aswel? Nightmare is the final boss on easy apparently. What??
Oh, and also: DLC characters being bosses is quite a dick move IMO.
Also also, locking Inferno behind the hardest difficulty is a dick move as well.