A family of Microsoft relational database management systems designed for ease of use.
Hi Spencer,
There is no out-of-the-box option to disable the Mark Complete button in the Tasks tab using the Permissions feature in Project Online.
You can check the list of available permissions to be given / denied with Project Permission Mode using the link below:
Category permissions in Project Server 2013.
Global permissions in Project Server 2013.
Alternatively, if you are using SharePoint Permission mode, you can check the permissions of each group using the link below:
SharePoint Permissions Mode default permissions for Project Server 2013 SharePoint groups.
As you are using a JavaScript Web Part as a workaround, we'd suggest posting in theProject customization and programming forum to see if there is a workaround regarding the 200ms delay.
Regards,
Sheen