If you hire developers who know HTML and CSS please rotate in some more interesting work for them.
Also be careful not to elevate the design team above people doing the HTML / CSS. Too often the design people go back and forth with a higher up until an "approved final design" that makes no sense gets thrown in the laps of the devs.
Today, by "design" people often mean "graphical design", which tends to attract more art-type people. But what is really needed is "UI design", which is a much broader discipline which involves art, technical stuff, and psychology. You need to think about "what looks good?", but also "what makes a good UI for our product", and "what can we reasonably implement without too much complexity?"
Certainly in my experience this confusion between "graphical design" and "UI design" seems to be a huge chunk of the problem.
So basically, I think you agree with the previous poster?