I just added the 'Edit Flow' plugin, and part of what it does is add additional status options (Assigned, In Progress, etc.) - MarsEdit does not seem to see these. I am guessing that you have hard-coded Published and Draft status options. But as it stands now, if I use the Edit Flow calendar, schedule a post and assign it to a writer, MarsEdit will no longer see that post unless I leave it in the draft status.
What chance is there that you could 'pull' the status from WordPress?