When I write an article for a website, I will often submit the content as a whole to a handful of article directories. Is this bad? Does this make the content on my site no longer unique?
Not really as long as the content has back links. But there are some instances that the original website is outrank with article directories which they submitted the articles. So try to change your content a bit to make it unique.
may i make a cheeky suggestion that may not be easy to implement, if you have the patience and can sort of sniff the next crawl of your website or that directory than best to submit just before then so that at least to the bot the content was seen linking to you first before thingmejigrobevery1 gets access to it. IMO, but it's hard.
Publish your article on your site and let it get indexed. Once its indexed submit it to the article directories. Don't change anything in the article it will waste time and chances are the duplicate content filters will discover the similarities anyways. To answer your question... your content will no longer be unique. So don't optimize an article with the same keywords you are competing for with your home site. A lot of these article directories will rank above you for the terms you submitted in your article.
i agree...wait for your site page with that article to be indexed page as if you'll let article directories with your article be indexed first you'll be penalized with duplicate contents....
it has been said that you only need to modify your article by about 30% to make it unique on your own site. ;-) good luck.