I really do not understand this line of thought.
Devs should of course write their own tests, however if you missed something in the code, perhaps you may miss it in the testing too? You need QA.
I have never seen flawless code and I have never been on a project where someone thought of everything.
I've spent too much time at war with a team that wouldn't use QA and yet their shit broke constantly. Even with their own tests.
That said every good dev should have a QA minded brain. I also don't like throwing shit over to QA to check your work either.
Some of us
have had jobs where we develop both hardware AND software.
arty