The four South Africans were Steven Kitshoff, Makazole Mapimpi, Lukhanyo Am and Lood de Jager, with skipper Siya Kolisi missing out.
Australia's McDermott was perhaps the most surprising inclusion, having started just three of the six matches with Nic White favoured in the second half of the tournament.
Several All Blacks backs who had great tournaments were unlucky to miss out, including David Havili, Beauden Barrett and Rieko Ioane, while Ethan Blackadder was perhaps the biggest omission from the forwards.
Other notable omissions were Springboks Malcolm Marx, Faf de Klerk and Duane Vermuelen.
World Rugby's Rugby Championship XV:
15. Jordie Barrett (New Zealand)
14. Andrew Kellaway (Australia)
13. Lukhanyo Am (South Africa)
12. Samu Kerevi (Australia)
11. Makazole Mapimpi (South Africa)
10. Quade Cooper (Australia)
9. Tate McDermott (Australia)
8. Ardie Savea (New Zealand)
7. Michael Hooper (Australia)
6. Akira Ioane (New Zealand)
5. Lood de Jager (South Africa)
4. Brodie Retallick (New Zealand)
3. Taniela Tupou (Australia)
2. Codie Taylor (New Zealand)
1. Steven Kitshoff (South Africa)