My employer develops safety critical software with decades of legacy code, long term support for multiple versions, and big customers. In our attempts to transition(in a mock way for the time being) to rolling releases we've "simplified" to a process with 3-5 people reviewing designs, 2-3 developers doing code review/light testing, 2-x(depending on affected modules) quality assurance people doing heavy testing and occasionally we pair program. Documentation/logistics is almost always more time consuming than design and development. I've had 4 character code changes take weeks to get through the process as several people have to find the time to look at it even for just an hour. It's cumbersome but we do catch a lot of bugs, and we're slowly getting better at design.