Regarding interaction with designers, I believe the answer is 'It Depends'.

As an example, in the Clojure space there are two libraries that are good exemplars of the ends of the spectrum: Hiccup and Enlive.

Hiccup (http://github.com/weavejester/hiccup) uses sexpressions to define the (ht|x)ml output. Effectively either the developer and designer roles are fused or the developer gets a design from the designer and encodes it into hiccup manually.

Enlive (http://github.com/cgrand/enlive) is (in overly simplistic terms) a selector driven substitution engine. You give it an HTML file for a template and some CSS selectors describing what to modify, alternatively you define a snippet in terms of some elements within the page. In this model the designers work is first class resource, and not modified by the developer.

This is exactly the same breadth of options as I've seen in just about any real language being used for development tools.

This is just one style, not representative of all Lisp web development. You can have any style you want. With continuations you can even use a procedural style where your program describes a workflow of multiple pages.

(Whether MVC is the right style is a topic for another discussion.)