Maneeza,
I'm aware of the limitations of tracking with non-local assets, but it's actually not the engagement score that's the problem- that actually seems to be tracking just fine, which was a pleasant surprise. It's the "unsubscribe" metric that I'm specifically missing in the dashboard. It's not a huge issue- I can still get to that data other ways, but it's an annoying limitation all the same.
Regarding the RCA question, I've essentially decoupled content from channel in my program design. If I have a new whitepaper, all the assets that relate to it are located in one central content program. If I want to use that piece of content in a particular channel, such as online advertising, I have a separate program for the channel that's used for tracking, and references the content program's design assets. Then, a lead is essentially a member of both programs:I can see that the lead converted on X channel, and meanwhile, that they also downloaded Y content.
So I can still do channel level attribution, but now I can also do content-level attribution. With this structure, there admittedly isn't a great way to look at content performance WITH channel in Marketo's RCA, but again, the structure I've pursued has benefits for me that outweigh this reporting limitation. Ultimately, I can can get at mutual program membership data via SFDC reporting if needed.