This is only anectdotal evidence, but I have 78,000 miles on my original clutch with no issues. A lot of that is on gravel and dirt, but nothing I would consider "off-road". I suspect that anyone doing a lot of actual off-roading on a 700 pound plus motorcycle/rider combination would experience a lot more significant clutch wear, even if they're a very skilled rider. I doubt that it has anything to do with a flaw in the bike, or even a flaw in the rider, for that matter; you're just asking a lot from the clutch of what's basically a street bike with minor off road pretensions rather than a purpose-designed dirt bike. I'm just speculating, but when Yamaha designed this bike, I really doubt that the engineers really considered that people would use it in the same manner that someone was using a YZ450. Just the weight, ground clearance, gearing, and the fact that the oil filter hangs down low off the front of the bike kind of backs that up.
I too was one of the ones who got stuck in deep sand once and never thought of turning off the TCS. I was down in South Carolina and got too far down one of their legendary sandy back roads. Just kept stalling it as I was trying to work my way out. I gave up trying to get out and was just about to walk back to the main road when a log truck happened along and the driver helped push me out of the soft spot I was stuck in. It never occurred to me until much later when I had one of those "hey, you moron" epiphanies that the reason I couldn't get out was most likely because the TCS was on.