if the articles are good - then there just might be value to the user . Depending on the niche / industry those old articles could be very important.
Google dosen't like those as you probably have a lot of impression but no clicks (so mainly no traffic) or maybe the "score" is bad (bounce rate - not Google analytics bounce rate, but Google's bounce rate - if they bounce to serps that is).
Since you got hit by panda, in my opinion, I see two options:
1. No index those old pages. The users can still get tho those by navigation, site search etc but google won't see them. Google is fine with having content (old, poor, thin etc) if it's not in the index. I work with a site that has several million pages and 80% is no index - everything is fine now (they also got hit by Panda).
2. Merge those pages into rich, cool, fresh topic pages (see new york time topic pages sample - search for it - I think there is also an seomoz post - a whiteboard friday about it). This is a good approach and if you manage to merge those old pages with some new content you will be fine. Topic pages are great as an anti panda tool !
If you merge the pages into topic pages do that based on a simple flow:
1. identify a group of pages that covers the same topic.
2. identify the page that has the highest authority of all.
3. Change this page into the topic page - keep the url.
4. Merge the other into this page (based on your new topic page structure and flow)
5. 301 redirect the others to this one
6. build a separat xml sitemaps with all those pages and load it up to WMT. Monitor it.
7. Build some links to some of those landing pages, get some minimum social signals to those - to a few (depending on the number). Build an index typoe of page with those topic pages or some of them (user friendly one/ ones) and use those as target to build some links to send the 'love'.
Hope it helps - just some ideas.