To fix this, I wrote a script that looks at the default printer and exports it to a registry file in the user's profile only if it's set to network printer on a specific set of print servers at my organization. At login time the default printer is restored. All network printers are exported and restored at logon/logoff too so they don't disappear by accident as we see sometimes too for printers not deployed through group policy.
This was especially important as we moved to using persona management, as this caused this problem to happen way more often on a floating pool.