We ran into this problem a while ago and found that it was quite a bit of overhead to set up workflow manager service for a dba to request if that is the only person that will use it. It is possible to run a geoprossessing service from a URL especially if they do not have any parameters.. It just takes a little research into the submitting requests using the REST API.
Yes, using the REST API is certainly a preferred option because of cross platform usability. I would suggest exploring the viewers available on the workflow manager resource center to see how these things are done.