Article links are worth very little as is, when you submit to multiple directories what little value that link is worth less... Why wouldn't this be the case? Article pages are generally orphaned pages or are deep into the site, they have no external links pointing to the page and yet a number pointing out. So article links are pretty worthless, unless you have a very good article in which case it should either go on your site or a industry leading site.

I wouldn't submit my articles to directories, why purposely create competition? It is my work, let them come to ME for it. I actively search out my work and I have it taken down if any of my articles are reproduced. I want my blog/sites unique and I want the people to come to me... that doesn't mean I don't allow people to use my work for reference...

Also contrary to popular belief the first copy to be indexed is not always, eternally seen as the original. The site with the most authority and links to their article generally are seen as the original... yours may have been indexed first but is it the most popular?

I had this problem over a year back... I started a new site, my content was all indexed, it ranked pretty good for medium competition and many long-tail phrases. Then one day an established site copied my whole site, every last drop of content was taken. Within days I lost most of my rankings for anything substantial and I noticed the thieves pages indexed.
Mine were indexed over a month before the thief stole my work... why didn't google see me as the original?
I had very few links, little authority and the thief had an established site, many links, authority and hence was seen as the original even though mine was indexed first... so contrary to popular belief indexing date is meaningless. I have seen this more than once.

Needless to say I had to start legal action against the thief and he did take it down... but it took a while before my rankings returned. Google really looks down on sites which copy the vast majority of their content from other sites.