Dempster would be fine on the Versys 1000, but I'd put a rad guard on for sure. South Canol would also be fine, North Canol, not so much, but that's significantly rougher. You could do it, but I'd rather take something else - like my Jeep, frankly, since packing enough fuel on a bike is an issue.
The Yamaha dealer is great, but so is Listers, who are Kawasaki and Suzuki - I think their mechanics are better overall. Honda/KTM dealer, not so sure, good parts, but haven't really used their service as all I bought from them was a Ski-Doo. They did take a buddies early model KTM Adventure back though, when it proved to be essentially unfixable, seemed the first couple years had lots of issues, so that was good of them.
Lots of great roads, and side roads, I'm going to explore some of the side trails off the South Canol this summer - Sydney Creek, Groundhog Creek, etc. Way too many places to go, and I keep saying I'll spend some time on side trails off the Stewart-Cassiar instead of blitzing south...