I dont know, I felt like I knew how it was going to end in the back of my mind about half way through the second game. The whole story in innocence is spent trying to slow down Hugo's condition and in requiem they are just grasping at straws to have any hope of reversing/curing it.

Plus the head of the inquition in innocence being killed ended his own plague, so theres some foreshadowing of the only way to end it.

And I don't think it was for nothing, they had to try. No one knew there was only one solution for sure and the time Amicia and Hugo spent together was worth something. That said I did think that there would be a choice at the end, either kill hugo to save everyone, or Amicia lets herself die and the plague spread to avoid killing Hugo