In the last Iron Butt there was a Victory Vison entered. I think that the stock bike weighs 900 pounds, but this bike was entered in the Iron Butt so it was carrying extra fuel and everything that might be need for two weeks riding any where in North America. Not the bike that most would choose to ride "off road".
There was a bonus location to Bristle Cone Pine forrest to vist the oldest living tree in the world. The road to the bonus is twelve miles of of rock, dirt and pot holes.
The fully loaded Victory Vision made the 24 miles round trip with no problems. It wasn't because this is a good off road bike, but because there was a real good rider on this bike.
This was a long way of answering your question about how "good" is the V Strom off road. My answer is it depends on how good a rider is on the V strom.