My last employer mandated a second Captain for an augmented crew, and we also had a Flt. Eng., someone with aviation experience on the flight deck who might just be thinking outside the box relative to a pilots' thoughts, and also wasn't physically involved in handling the hardware in the same manner as the pilot, so could look at a problem from a different angle.
But that costs money, and we must always genufluct to Progress.( and profit )
The last words recorded from another accident where the pilot was confused as to the information he was receiving was - look at the standby ( which was giving the correct info. ) shouted by the F/Eng. Too late unfortunately, which of course raises issues of P.C. culture and CRM as well.