I don't use FB for marketing (barely use it for anything anymore) BUT - the businesses I have "Liked" and "Followed" get me to visit by talking about new content or sales so I can get more or better info by visiting than from reading their FB posts.
Seeing as FB is not showing your updates to most of your "fans" you want to only post things that will get shared and liked by whoever might see them and that goes double if you're paying to get them seen.
You are indeed correct, I should have said that it regards a few lines (Call for action) with links to article (no sales involved) but that intro I would like posting on FB is the same intro than the one residing on my site, thus Dupe concerns.
Sometimes it a good idea to use Facebook as either a general news outlet for your business or as a place to summarize and direct Fans and potential readers/customers back to your website / sales pages. Fresh, new high quality unique content is always a good plan as well to start producing results.
People who hang out on Facebook generally will probably not see the content on your site. So I don't have a problem posting content on your site and then posting it on your social media profiles, as well.
As far as SEO is concerned, Google indexes Facebook pages--so there potentially could be an issue. But why not just post "part" of the content on Facebook, with a link to the rest of the content on your site?