He wouldn't have lost relevance if he had lost, but I don't think he did himself any favors with his performance. However, this was just a bad fight for him to take at this junction of his career because the expectations are set way too high for a guy that's a 20:1 favorite. Cormier would have had to perform a Mortal Kombat Fatality on Staring to impress people.
I thought he looked pretty damn good. It had to be hard getting fired up for this fight, which did absolutely nothing for his career, but could de-rail it. He totally dominated the guy and finished him. Not sure what part of his performance didn't do him any favors.