Hi Geoff,
I have a nearly new V Strom 1000 and on long runs, 300 miles plus, I used to get a numb throttle hand. This was cured by fitting Grip puppies and loosening my grip a bit. I rode home last weekend from Inverness to Northumberland with only one stop for fuel and a Mars Bar with no hand numbness. My last bike was a VFR800 FI which was not vibe free but the Strom took a bit of getting used to compared to it.
Try the puppies, they're cheap and it could be the fix you need.