Recently, I heard an announcer during a NCAA game mention that he didn't like his players to have too many steals; he believed they were taking too many chances and were prone to more fouls and reaching.
He didn't mention the same for blocks, but its been said that guys who go for too many blocks are prone to leave there man more.
This probably comes down to the individual player but in the Warriors case Curry and Monta get plenty of steals; but I think we all agree neither are good defenders, although Monta shows flashes. (To Monta's credit its hard to be the focal point on offense, play 40mins per game, and play hard D.)
Dennis Rodman Tayshaun Prince Arron Aflalo
These three guys are considered good defenders, none of them have averaged over a steal or block a game. (in a season)
That being said, I still believe steals and blocks are important, but just because you rack them up doesn't mean you play good defense.