A lot of people use “designer” to include that personality, but just as often, web designers are so focused on appearance, and neat tricks and tools, that the product is a great looking site with a weak message. And many web designers are strong in visual, graphic modes, and not very effective writers.

Not every business or web site owner can write, so sometimes an outside writer (or an employee that truly has those skills), ends up handling the content. That “Communicator” has the job of taking in a lot of guidance from the Strategist and the Marketer, and turning it into content that will make a difference to the user..

As a client once put it to me, “A good writer says exactly what I would say if I knew how to say it.” In the end, people keep returning to your site because you say smart and useful stuff, and this is important enough to have another “personality” explicitly paying attention to saying things well.

The only thing I don't necessarily agree with is finding a designer on 99 Designs or Crowdspring.

I'm not sure those are really good places to find designers that are good strategists, which they really should be as well as provide the “window dressing”.

In my mind, that's what being a designer is all about. Strategy and finding good solutions to problems.