I don't really understand why fields and workflows have to be tied in together. Is it because some workflows have transition screens?
Sometimes the are fields associated to validators/conditions/post-functions, but does are not the only fields being created at the time of an import.
Anyhow, if this is by design, there is something I don't understand about the usage of a "dev vs prod" JIRA.
In order to keep our production JIRA stable, we require people to experiment in our test instance before doing any change to the production instance. What we do is regularly update the test instance with a copy of the prod JIRA database, so the two systems are nearly identical.
When we developed new workflows and tried to import them in the prod instance, this created *dozens *of duplicate fields (I'm not exaggerating). The behavior of JIRA when deleting fields is very painful (you can only delete fields one at a time and the page reloads after each deletion) so it's a tedious task. Also, some statuses and screens are duplicated if I'm not mistaken.
This is very frustrating since both instances shared the same fields of the same type with the same ID and the same configuration. 
We are now obligated to develop directly on the production server, but we are much more restrictive on the number of admins in the production instance.
You could at least have an option to "Not export anything" and let the import process do a best effort to match things.
Workflow import/export is not currently available in Cloud