suggy - 7:37 am on Dec 31, 2011 (gmt 0)
Could it be that what you are doing is increasing the uniqueness of the page relevative to others on your domain?
On my commerce site, I had five sections covering one brand (eg brand widgets, brand wodgets, brand wotsits, brand gizmos, etc). Each sub section was entirely plausible, covering a different sub-type. They all sank in April Panda (UK site).
I have been gradually deleting the sections and with each delete comes a rise in the rank of the overall/ umbrella section, which is now back in top 5 places.
This would fit with Google's aim to kill content farms, who tend to have many overlapping articles.
You shouldn't just test for uniqueness in www terms, but also on your site.
BTW, having unique content for each is not enough. I tried that. You just cannot get away with having many pages on same topic, even if technically unique.