Steering at very low speeds with a single finger might be slightly unrealistic with these machines given their weight and the steering wheel diameter (not to mention the wheel needs a fair bit of twirling going from lock-to-lock), but the physical input shouldn't be anything that could be described as exertion. Have you checked the power steering fluid level? Insufficient fluid in the system won't allow it to provide enough pressure for the proper amount of assist. If it's any lower than the max line I would first top it off, then check the condition of the system hoses.
This generation of RR incorporated ZF's Servotronic variable power steering assist; a valve in the steering box controls how much power assistance is administered based on vehicle speed (the higher your speed, the heavier your steering becomes) and in my experience allows for ideal vehicle behavior in most any situation when functioning properly. It is fairly common, however, for the Servotronic valve to seize up (though when this manifests itself as heavy steering it is most often after a period of high speed driving where the valve refuses to move from the low-assist position one you've slowed down), so I say it's a good idea to have your dealer or local Land Rover/Range Rover specialist check the component for faults. Also, as electronics govern so much on these cars, a computer reflash is probably in order.
Also, does your vehicle have the standard 19-inch wheels or the optional 20-inch items?
Such is life: sometimes, you are the bug; other times, the windshield.