Any Pilot worth his/her salt should know the approximate engine power setting for an approach with whatever flap has been selected and should be included in the constant scan regardless of whether the thrust levers move or not when auto throttle selected.
From my B767/757 days I cannot recall ever using V/S mode and was always told of its dangers. Don't know anything about the B777 which seems to have an inherent problem for those pilots with a lack of awareness of what is going on around them ie airmanship.