Defence does indeed win Premierships, but you need points to back it up that's for sure. Sharks are a prime example of this (as were the Broncos, but recently our defence has been shithouse as well).
The strange thing too is that the Sharks get a ton of offloads away, and a lot of them are to advantage. The fact they so rarely score off any of them and rely so heavily on Carney really goes to show have inept their spine and outside backs are.