Though Death knights do have a few Rohan Gold silences and interrupts of their own, the addition of this on-demand PBAOE silence is still a nice (and flexible) tool for your DK arsenal. It can be used offensively or defensively, and with zero resource cost, there is no downside. More and more instant spells are being added to the game all the time, and silences are the only way to stop them -- this one will definitely win you some games all by itself. Slight extra points here because Death Grip will help DKs land this more often.