Obviously pragmatism is always important and no advice applies to 100% of features/projects/people/companies. Sometimes the test is more trouble to write than it's worth and TDD never worked for me with the exception of specific types of work (good when writing parsers I find!).
If you make logical error in the code, chances are you will make logical error in the test that tests that segment too.
A big problem with tests is making sure they are correct.
Would having someone else write the tests catch more logical errors? Very possibly, I haven't tried it but that sounds reasonable. It also does seem like that (and the other things it implies) would be a pretty extreme change in the speed of development. I can see it being worth it in some situations but honestly I don't see it as something practical for many types of projects.
What I don't understand is saying "well we can't do the really extremely hard version so let's not do the fairly easy version" which is how I took you original comment.