My thoughts are you can never have too much weaponry, was the Doubtless the lead ship regarding the testing\evaluation of Viper? Could it be that complacency dictates that the system is so good it does not need CIWS? Viper may well be the all singing, all dancing latest, state of the art system but Murphy's Law will always out trump your best hand and when you need a viper to send a message, Mister Murphy will intervene and that to me is when you NEED CIWS secreted up a sleeve.
Other posts have suggested this ship deploy just off a coast to be the most effective!! I am of a different generation but to me warships working close to a coastline are possibly not playing to their strengths.. Look no further than the Falklands, brave men that knew they were putting themselves into harms way.