Designs created in a vacuum will blow your development budget through inefficiencies, rework, and expensive customizations. When Ux, design, and technical resources work together to define a component based, user-focused architecture development hours are optimized and issues are identified and resolved early in the process. Involving Ux and design when building the author experience also ensures that you Drupal implementation will be easier to use and maintain.
Engaging the entire project team throughout the project phases not only captures diversity of though, but also allows cross-sharing of skills and ideas that help less experienced team members grow. When all team members are involved in the business analysis, sprint planning, estimating, architecture, and more, the team is more effective at designing solutions and solving problems.