Could not load file or assembly ‘DotNetOpenAuth.Core

If you don’t want use OAuth, remove references: both the WebPages OAuth DLL (I think it’s Microsoft.Web.WebPages.OAuth.dll ¹) and DotNetOpenAuth DLLs.

¹: You can find the filename in Calling assembly. So, removing all calling assembly of DotNetOpenAuth.Core should work for you. This approach should work for other unused missing references.