The goal here is to create a complete staging environment for building out major changes across your systems without affecting the production environment and then to be able to push those changes to production.
It needs to mirror production, e.g., staging website syncs to Marketo sandbox syncs to Salesforce sandbox, so that proper testing can be done.
The setup described above is what I have used before, which worked well, but I recall sometimes I ran into trouble when refreshing the Salesforce sandbox. The Org ID changed, integrations broke, etc. It was fixable but a pain.
Another setup I have seen is Marketo sandbox syncs to Salesforce developer org. However, the increased difficulty in pushing changes from one org to another means it is more of a playground/testing environment rather than an actual staging environment, meant to replicate production.
Just curious if anyone has any other setups that are more optimal.