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It's really a process of experimenting over time to find out the method that results in the most URLs indexed that in turn brings the most relevant traffic.  Personally I wouldn't have one for each category, yet without tests there's no conclusive reasoning either way.

Jarrett, the canonical tag you have in place will suffice. I'd suggest either to have users moving between the sites in the future or to modify your CMS to auto add the canonical tag in any future posts. It might be worth speaking to your syndication partners and changing your API to only show an excerpt with a link back to your site. This will also eliminate the duplicate issues and allow more of your pages to rank. It's highly unlikely for you to get your larger media partners to add a rel=canonical to your posts on their site as they simply don't need to, as they are more likely getting the content indexed. Aaron

I have a client who saw big drops beginning the 11th even though they're U.S. based.  A portion of their visits come from international sources.  We're still in evaluation mode though because the site had no significant drops on the initial Panda update here in the U.S. Preliminary checks of other data show it might partially be a Panda issue, but not completely - oddly enough beginning on the 11th they also had a serious lag time in content loading due to advertiser scripts, which I'm thinking is a big factor as well. Something that I have been speculating on with several new clients is the gradual degradation concept.  My theory is many of their links coming from other sites that got hit has caused a rolling drop effect.  Since none of my longer term clients have seen any significant drop though it's a more difficult assessment.