Under every other circumstance, I'd agree with you, DJ. You know me--I'm a stickler for theme. Everything for Lovecraft. It got to the point where I don't like August Derleth or what he did to the mythos--he turned unknown horror in pulp horror, something Lovecraft barely did, if ever (the closest being The Color out of Space and /maybe/ The Whisperer in Darkness). These are terrors that like you said, cannot be understood by the human mind, and victories in Lovecraft were achieved usually by accident if ever there was a victory at all. Its why I don't like the idea of out-of-theme Investigators, Heralds or AOs in the fan-mod stuff because it is simply too far removed from the theme.
Curse you, August Derleth.
To the point, though, this is a boardgame. And while 'fighting' the Heralds may be out of theme, the concept of combatting their effects is not. Actively seeking out solutions to stop the evil, like Armitage did with the Dunwich Horror, is something that Lovecraft allowed, though, like Armitage stated, sometimes the cure was almost as bad as the disease. But people DID fight off these horror. In Dreams of the Witch House, the narrator choked the witch to death on her own 'realm', despite all her powers. He managed to refuse Nyalarthotep's call. People CAN resist the mythos so maybe, yeah, the idea of the Tokens moving from their given spot is a bad idea but the notion of the Investigators outright denying the heralds and ancient ones is absolutely not out of the question, even to a purist. Despite all his morbid stories and the ideas of how tiny man is in the universe, Lovecraft was, in his own odd and nutty way, a optimist when it came to what humans were capable of doing.