In my experience, a good Data Migration team will prove themselves to be a key component to the to all aspects of you application delivery. Vendors are required to deploy stable and correct application & metadata builds. System integrators are required to work with these vendors to ensure environment builds contain the correct application and metadata builds at the right time.
Vendors should have a strong, repeatable application build process to ensure that each environment build contains the correct metadata build, application build, indexes, sequences, foreign keys, etc. What if the environment build does not match the release note they produce?
A good data migration team will define their own set of environment acceptance tests to validate each environment build. They can use their intimate knowledge of the target database to validate sequences, indexes, foreign keys, table spaces, and metadata configuration for each environment build. Missing indexes, foreign keys, etc. will often result in significant performance issues or fail transformation rules and can be quickly detected. Data migration teams will often use parts of the application for their own test cases and can therefore also be used to validate the application build as well.
Do not underestimate the capabilities of your data migration team. A strong data migration team will likely be willing to help identify issues with the environment builds to aid the overall solution delivery, as well as their own.