Dev writing automation tests for their code is kinda pointless. It would be better to have another dev or a different team such as automation engineers writing regression automation tests. Automating regression tests is definitely better than manual QA-ing the same 1000 tests over and over again. There has to be a good balance. Have extensive coverage of automated regression tests and let manual QA test new features. This will at least increase the frequency of release cycles. Getting rid of an entire QA dept is somewhat equivalent to shooting yourself in the foot.