Not necessarily: he has to to kill the person playing "Argos" because, in the story, "Hermes" kills "Argos." Which is what sets "Io" free. So, presumably, his reasoning is that Asterion is in captivity, making him count as "Io" and then freeing "Io" will undo that. If that is his plan, and if it works, then presumably nobody else has to die.
So I guess in this case, the role of "Hera" would be Athena? As the architect of "Io"'s captivity whom Hermes is thwarting.