This scenario makes sense and it gives you more security. 

**Why use WAP on-top of SharePoint & ADFS?** 

Because it gives you a way of exposing your public SharePoint applications to the internet without anyone having any line-of-sight. This is important because it means nobody could overwhelm your SharePoint infrastructure without being authenticated first.

Read more about 

- [Publishing SharePoint with Windows Server 2012 R2 Web Application Proxy][1] 

- and [SharePoint Server and Web Application Proxy – continued][2]

on Windows Server 2016, please read this

- [SharePoint + Web Application Proxy – 2016 Edition][3]


  [1]: https://blogs.msdn.microsoft.com/sambetts/2014/12/10/publishing-sharepoint-with-windows-server-2012-r2-web-application-proxy/
  [2]: https://blogs.msdn.microsoft.com/sambetts/2015/07/01/sharepoint-server-and-web-application-proxy-continued/
  [3]: https://blogs.msdn.microsoft.com/sambetts/2017/04/04/sharepoint-web-application-proxy-2016-edition/