This card would be a lot better if the first sentence instead read like this:
"Parley. Choose any amount of enemies at your location and test (Book) (X), where X is the chosen enemies' combined damage/horror values."
The way it is right now, it's only usable in specific boss encounter scenarios on enemies that deal 4+ combined damage/horror value, and even then you also have to succeed on a 4 difficulty test. Of course, it feels like a 5 XP card when it's in that specific case, but that makes it a niche purchase.
If the text was written just slightly different, you would be able to more consistently get the 5 XP payoff from this card, not just on boss enemies. If you were able to select any amount of enemies, you would have the option to make your test harder, but deal that much more damage in return. Sometimes you want to deal with thicker enemies that have 3-4 health, but they're not bosses or deal little damage (hello, Coterie Enforcer).
Plus, there is a downside to the upgrade where in some situations you would be able to deal more damage with the level 0 version, by using it on an enemy with 1 damage/horror value.