[J-WO]

A spirited and well-argued defense.
Now, I haven't read it in a while (In fact its high time I returned to Lovecraft generally--I'm always spouting off on this forum so I've really no excuse these days) but I've always felt that Dunwich does contain unadulterated cosmic horror, yet cleverly obscured by the ill-educated, yokel Whateleys, who act as a kind of filter.
They live in a remote environment, are essentially raised in a Judeo-christian culture-at-large (rebelling against it as they are), and their understanding of what they're doing comes from the works of Alhazred and the like--writers from earlier, even less scientific times. None of them could tell you slightest thing about quantum physics, say.

For all we know, there may not have been a need for human blood at all, initially, it was just the sort of thing all of the above mentioned would think you'd have to feed the Old Ones. Maybe it just provides some psychic focus for the summoners. And then old brother-in-the-barn gets a taste for it. Such gibbered confusions (especially that whippoorwill thing) are the source of much speculative delight for the reader.

The nearest example I can think of is Machen's White People- with a parochial, uneducated person telling us things they can't satisfactorily explain. Its an effective tactic towards creating something eerie and, as far as having human participation right next to the alien and inexplicable, you can have your cake and eat it.

So, yeah, very fond of this tale.