That sounds odd. The way it was done in every place I worked, is that a set of changes were approved for a release before they were planned and implemented. We organized the work as expected: each bug/feature on its own branch, with its own set of unit tests, etc., and automated testing applied on each commit. These branches are then merged to the integration branch once they are known good. Before the release process starts, QA would get a copy of the integration branch and test that.

The dependency problem doesn't exist, because all the features were already approved to be in the release. The only way there would be a problem is if someone decided late in the game to pull a feature and that feature was a dependency to something else.