My team, 2468, rigorously CADs every component of the robot to ensure smooth integration and communication between the design and manufacturing teams (which are distinctly separated on the team).
However, I know that some successful teams like Cryptonite (624) doesn't CAD their robot except for few parts that require CAM. They seem to do well every year anyway though...
https://www.youtube.com/watch?v=adkAmveee6k