I have created program for each piece of content. Every program contains the emails, pages, triggers, and so on. I measure success (progression) in each individual program. These could also be synced to a SF campaign of course. The engagement program uses a smart campaign in the content program to send the email.
Another way to track everything is not to use a program in an engagement program, but directly the email from a content program, but inside the content program there is a trigger the tracks the progression of the conten tprogram.
Lastly you could create a folder with one trigger for each email you have (for your engagement program). That trigger fires on success for that item and updates the coresponding SF campaign.