Some of your content might be written by real authorities, but it's still lightweight and relatively thin. Compare it to Wikipedia if you want to see the standard you have to meet.
Even if you do manage to game Google again it's likely you'll get slapped down in a future tweak. It's an arms race and they're not playing around anymore.
Build something that's strong enough to stand on its own.
My site is cited by numerous museums, libraries, and reference sites as being an authoritative source for information related to my industry. And after reading your comment I looked through Wikipedia for several hours and my site is one of the most commonly referenced and cited resources for my subject matter. For example: http://en.wikipedia.org/wiki/Baseball_cards http://en.wikipedia.org/wiki/Topps http://en.wikipedia.org/wiki/Upper_Deck_Company http://en.wikipedia.org/wiki/Rookie_cards
With all that said, since we cover niche news stories the length / depth of the content is dependent on the stories themselves. For instance, if a company releases an updated checklist for one of their sets, it may only give me enough information to create a 200 word article. But since its information that is both helpful and relevant to my readers, I publish it anyway. Maybe its time to cut that portion of my business out though and double down on other types of content so that I don't have news stories pulling the rest of my site's content down.
My reference to Wikipedia was to the quality of their articles.
I know they're not exactly the same thing, but look at these:
http://en.wikipedia.org/wiki/T206_Honus_Wagner
http://www.cardboardconnection.com/baseball/t206-wagner-card...
All your content appears to be about this thin, and you have tens of thousands of pages like this. That's what a content farm looks like to me and Google.
So thank you for your insight, and thanks to everyone else for their feedback as it has been extremely helpful.