Back in the time of target designation being made by map coordinates given by a very scared guy on the ground (no gps) and either a smoke grenade or perhaps some tracers or muzzle flashes.....or at night tracers or verbal directions and visible light strobe lights/flashlights....there was some discussion as to the effect of having two pilots in an enclosed cockpit versus having two door gunners as well had on efficiency in acquiring targets.
With the advent of hi-tech means of locations, nvg's, FLIR, etc......the two pilot gunship has come into its own!
The USMC also uses their latest UH-1 for gunnery Support as I hear it.