I'm definitely a fan of only syncing 'success' statues as defined in your Marketo channels. For communicating with sales, if you have workspaces, you can always send them your emails as well so they can see what the message was and who you were sending it to. Alternatively, you can add a decent amount of this information either into Sales Insight or into the campaign itself.
I've had similar requests from my sales team and, much to my chagrin, I was managed into syncing those activities into the SFDC Activity History. As a result, my Market account manager is going to train them on the benefits of using MSI instead. In many cases, there is no reason for them to know those details outside of MSI (although if Marketo marks an email address as unmarketable, I create a task for sales to follow up as part of cleaning data).
As far as communicating with my sales team, I comment on the SFDC campaign with all the details they need (including the landing page) and mention the appropriate sales groups. I then typically add all members to the campaign for their review. We try not to send any email outside of Chatter, so I don't bother with that step.
I think you're going about this correctly! Has your team been missing important info or asking for more?
Thanks for the input. I agree that MSI should be enough. Rather than adjust the syncing beyond program successes, I will educate them about the Marketo Lifecycle Status value of "Engaged" so they can use that status to help them prioritize outreach to prospects that are more that have taken some action. They can then add that into call lists/reports into SFDC.