<file>style.css</file> this syntax is for css files that are in the skin folder it does not need or use virtual path attributes cssvpath or imagebasevpath, the virtual path for the skin folder is already known from the syntax. The use of those attributes is only for when the css files are not inside the skin folder, like if using css from a common shared location
You should not have to hard code any virtual path attributes that point to a skin folder because then it must be updated if the skin is renamed or moved to a different site.
I personally do not recommend disabling CSS combining. If you do that then there is no control over cache and skin guid reset is irrelevant, plus you need to make sure it does work with css combining before deployment to production and people too often forget to re-enable it so they end up with lots of extra http requests in the page for each separate css file. You can disable minification and caching on your dev machine but I would not disable combining CSS. Generally you can figure out which css file a style rule is coming from by its location in the output css and the list of css files in style.config.
Hope that helps,