Indeed, code coverage is a very poor indicator of anything useful.

For one, its focus is unit tests; but for highly distributed real time systems (which most are today), unit tests do not tell you that things work. One also needs component level tests, and system level integration tests, and concurrency tests (since systems are real time), and failure mode tests (because things go wrong in distributed systems). But code coverage addresses none of that.

Mutation testing is a powerful technique if added to one's overall test strategy. Here is an article series about defining a test strategy: http://www.transition2agile.com/2014/12/real-agile-testing-in-large.html