This problem could be solved with better editors. You could switch between "programmatic mode" (with all variables and fancy stuff) and "view source mode" (with variable values and plain CSS in general) with one keystroke.

You could also have semi-programmatic modes that show some programmatic features and "expand" others. Also it would be possible to look at the plain CSS but have values coming from the same variable in a distinct color.

We should get more creative with multiple views of the same document in the editing department.

Sass actually takes pains to make the source code it outputs readable. This isn't always entirely possible, since by its nature expressing something in Sass can take significantly less code than the CSS counterpart and properly organizing the expanded code automatically is hard. But there are several output styles designed to be readable, and it's possible to add comments that are rendered as CSS comments.

I love the compact output style (Sass::Plugin.options[:style] = :compact) to tell Sass to outpus one-line CSS files.