This strategy is essentially the same as everyone elses. I use a similiar strategy but I automate my first tier web 2.0's and I don't bother writing a unique article for each web 2.0.
Have you tried writing 1 unique article and syndicate it over your 1st tier web 2.0's? I'm guessing you would see similar results. Just change the position of the anchor text. If you could achieve same results, you would cut your time down drastically.
If that's successful, you can move on to try and syndicate your social bookmarks.
Could be a fun case-study.
I have a keyword sitting on #5 place, 4400 exact searches/month with only syndicated content.