Article Submission - dupe content, backlinks and effectiveness

Quick question for those with real experience.

I'm using articles for backlinks (what else!) and understand that duplicate content isn't so much about penalising a site by Google and more about just not getting the dupe content indexed.

So, to up my game article marketing I am using a submitter.

I'm taking, say, 10 articles and submitting the five best (sometimes all unique by me, sometimes spun, sometimes outsourced) and submitting to my favourite five article directories. Then I am taking the other five and banging them up to as many directories as my submitter will allow.

Not saying what I use, but it excludes some of the best directories and I am about to change to Article Bot - any views on that? I hear it is the best.

So, am I right to think that my unique content articles (to the highest PR directories) are doing me a world of good (my link reports suggests so) and that my directory 'spamming' with my lesser articles is giving me lovely backlinks without doing me any harm on the dupe content?

I am relatively confident that all is well, but wonder if anyone has a view?

BTW, I balance these link surges out with plenty of comment, forum, web 2.0 etc linking too.

Ian