It sounds to me as though you might be expecting the web designer to be both a designer and a frontend developer. It's critical that any web designer knows enough about HTML/CSS to know the limitations of the medium and what they can design but not necessarily enough to code it.

I think ideally, both the designer and frontend developer should be capable of slicing up a PSD. I'm a frontend developer, and I prefer to do that myself so I can save things in the optimal sizes and filetypes for my workflow. If the designer does it, they will be creating slices based on their opinion of how the website should be coded.

I don't think the responsibility for JavaScript is a gray area at all, it falls on the developer. It becomes a gray area when you remove one of the pieces of the puzzle, the frontend developer.

I also don't think your photographer analogy is fair. A photographers job can be defined as a person who takes photos. A designers job is most often defined as someone who creates designs.

It sounds like you're more of a backend developer, wanting to use a designer as a designer and frontend developer. You'll probably save money and get a better result if you have the designer stick to design and higher a third-party to quickly slice and code your PSD.