I'm actually wondering if Vezax couldn't be solo'd eventually by a hunter. The mana mechanic is negated, and without that it's basically a tank and spank.
Razorscale seems a good candidate if you are mindful of the enrage.
As far as level 80 heroics, I know on my protadin at 80 I was able to solo a vast majority of them. On beta I solo'd a few things as a hunter when I was playing around. I imagine most of them are possible at this point.
