Considering the stock went up 150% would say so, from a PR point of view, definitely not.
"But Yahoo’s turnaround remains very much a work in progress. Although Yahoo’s stock price has soared by a whopping 73% since Mayer become CEO, that gain is almost entirely attributable to investments the company has in two Asian companies, the Chinese e-commerce giant Alibaba and Yahoo Japan. Yahoo’s core advertising business remains sluggish amid intense competition from rival Internet giants like Google and Facebook."
http://business.time.com/2013/07/16/yahoo-ceo-marissa-mayers...
If Yahoo!'s advertising revenue had grown increased at the same rate as, say Google's (up 15% over the past year), revenue would have been ~$600m higher.
It's interesting that de Castro started out at McKinsey. The book 'Dangerous Company' portrays McKinsey consultants as Powerpoint jockeys who are great at formulating high-level strategy but not so good at actually running businesses.
Perhaps de Castro benefited from a rising tide at Google but lacked the turnaround skills required at Yahoo!