The markup should be strictly independent of the design!
All the designer should need to do to the .rhtml files would
be to tweak class attributes and other minor changes for the
purposes of identifying particular divs and spans.
As a designer, I whole-heartedly agree that all presentation should be
in the CSS file(s). However, access to and the ability to structure
the templates is just as important, in my opinion. For one thing, the
more “advanced” table-less layouts – rounded corners, for example –
point-of-view, so having the ability to set-up the page structure like
this is very helpful.