Wayne, I think you are exactly right. The very first thing that needs to be determined is the purpose of the Website. A business Website will be different from one that is a blog, or strictly for presenting information.
For a business Website, creating a positive image is going to be number one, in my opinion. This means, it has to look good. Good design, attractive, and eye pleasing. An ugly Website will do nothing for a company's image, no matter what information might be presented. Ugly says "cheap." Ugly says, "we don't care about our image." There are far too many ugly Websites out there.
"[C]ore marketing elements," yes! It's an advertisement first (perhaps I have this view because I took commercial art, and have a little advertising training, but I think I'm right about this). So, we have to create a positive first impression (company image), and then we have to "sell." Make it clear what the product or service is. An effective headline (the purpose of the headline is go get attention) should make the reader want to read the first line of copy.
Answer the question, "What's in it for me?" What is the product or service, and what will it do for me?
Short body copy, not too much to read, but creating the desire for more information. Call to action. "Call us today ... " Photos, more information can be provided on additional pages if necessary or desired, but the Home Page needs to create an initial positive emotion geared to getting a response.
I like to have some contact information on the Home Page (phone number) but I like to place a contact form on a "Contact Us" page.