We are an Office365 institution and we use Office Mix to deliver Training, Presentation with integrated Assessments, and other interactive material.
Many of you may have noticed that Office Mix will be transitioning to Office Stream and integrating into PowerPoint directly in May 2018.
I took the opportunity to reach out to Microsoft regarding their LTI and gradebook integration. Their response was that they have no plans to create an LTI for Stream. Which means that if you are using Office Mix as a form of assessment that you will need to migrate to another product or method.