I had some success with deoptimization of for certain keywords on my pandalized website in the following way:
Before Panda, I used to make separate pages for each product I write about, and I ended up with a lot of similar pages (since the products are similar) with different main keywords (product name) in the title tag, h1, alt, etc.
Then, I merged some similar products in a single post, with title tag, h1, alt, etc containing something like "widgets X1, X2, and X3 by manufacturer A".
After that, I'm ranking very well (1st SERP page) with these merge pages for queries such as "widget X1 by manufacturer A" or "widget x2 by manufacturer A".
For a page with only "widget X1 by manufacturer A" in the title, h1, alt etc I'm pretty sure I can not rank anywhere in the first 1-3 SERP pages, although these pages are optimized for a single product, which was better I think in terms of optimization before Panda.
Also checked some Google support docs and found that my changes were completely in line with the following advice:
"Minimize similar content: If you have many pages that are similar, consider expanding each page or consolidating the pages into one. For instance, if you have a travel site with separate pages for two cities, but the same information on both pages, you could either merge the pages into one page about both cities or you could expand each page to contain unique content about each city."