Its funny that you don't think that the 705s are a capable off road tire. While other issues are probably going to prevent me from mounting up another set, I've always found them to be a more than capable dirt tire. In fact, I was out with a buddy today, and he has 705s on his Wee Strom. I have to give him credit...he handled the deep mud, water crossings and technical sections of the trail very well.
Me, on the other hand, chose a bad line and tipped over in the mud. With TKC80s.
It ain't the bike, it ain't the tires. Its the RIDER.