Ballast for the portfolio – Bonds, Gold or the USD?

A common portfolio weighting known amongst many investors is the 60% stocks, 40% bonds portfolio. The general idea being that stocks appreciate in a bull market, while bonds keep their value in a bull market. Therefore, if you were long 40% bonds, you would have somewhat had a ballast for the drop in stock price. As of late, however, we have been associating the words “safe haven” and phrases such as “investors flee to safety” with assets such as Gold and the US Dollar. Have bonds lost its relevance as ballast in a modern investor portfolio?