How do I see a SAML response?

Hm..this is really strange. What version of BIG-IP are you using here? Are you doing SP-initiated login(going to the F5 Virtual Server first, or are you doing IDP-initiated from the ADFS? If you are doing IDP initiated, can you try SP-initiated? If you are trying SP-initiated and it is not working, probably worth opening a case with support to have them take a look at the overall configuration - something must be misconfigured somewhere...