High efficiency work vehicle drivetrains containing variator assemblies are provided. In one embodiment, the work vehicle drivetrain includes an engine, a variator assembly, and an auxiliary power takeoff (PTO) shaft, which is coupled to the engine and rotatable about a primary power path axis when driven by the engine. The variator assembly includes, in turn, a variator motor and a variator gearbox. The variator gearbox contains a planetary gear system, which is coupled to the variator motor and to the auxiliary PTO shaft. The planetary gear system is rotatable about a planetary axis substantially parallel and offset from the primary power path axis.