23 hours ago, Onidsen said:

Fair enough.

I got a response from FFG and the verdict is in. You do have to exhaust a separate character or declare the attack undefended. They acknowledged the fact that it was unclear and it's going in a future FAQ/errata. So for now, I'm treating the scenario I beat (Journey Along the Anduin from the Core set) as a win, which is great because I remember that one of my heros would have died from this attack.