Karina, I am not sure about this, but perhaps you could pull the list of hard bounces based on which campaigns they bounced for, and then do some kind of flow step to mass change their values? I've never done this before, but I've seen it posited as a solution for other similar issues.
Dory, other than what you suggest, are there any articles or help resources to address email deliverablity and smart campaigns to address them? I need a step-by-step breakdown of how to do this, why to do this, and how it affects leads in the system. All this information is so buried in Marketo's resource guides but it seems like a common campaign everyone else has set up. Why isn't this a part of everyone's onboarding?