[feverishaaron]

UX Designer (at Google) here. I feel your pain. For any design to work, it needs to be grounded in a firm understanding of the user's behavior. I agree that design intuition is limited by one's own view of the world, so it's critical to gather the right data before going further than speculative designs. This can be accomplished through a variety of means, but observation and qualitative interviews prior to "design" are usually effective.

The design should be validated with different users from the same cohort prior to building it. Functional prototypes work well here. Ignoring user feedback here is a huge mistake on the part of the designer. Design is relatively cheap, and it's easy to iterate and check your assumptions with users before anything is set in stone. Correct me if I'm wrong, but this step would have increased trust with your engineering team. Often due to ignorance, some designers don't appreciate how much effort goes into these builds, and how early architectural decisions shape the product in ways that make it difficult to change later.

Acknowledged, that this is a "perfect world" scenario and business pressure might require augmenting the process. An experienced designer would understand how to do this and still get meaningful results.