Well, if it's like the druids believe and there's magic in everything, even if only a small amount, then maybe Demon Hunters could see everything based on their magic vision? I mean, I don't see Demon Hunters walking into trees and tripping over rocks and roots every time they walk, and going the wrong way without the slightest clue all the time.
I'll also say that like the guy in that video, that blind people still retain their senses, and actually have more training in living on the four they have.
Just because they are blind, doesn't mean they have to walk around with a dog or a stick to find their ways around... or to fight.
Quote:... In return for this sacrifice, the demon hunter gains the ability to see the world without vision — creatures are visible as dimly glowing forms against a gray and murky background. Demonic energy blazes like burning pitch in the night; the demon hunter sees and recognizes it easily.
There you have it. So being a demon hunter would be like seeing everything as a ghostly greyscale, unless there's a demon or possibly a mage or warlock around.