On the contrary, I see a lot of magical elements in the demon hunter; they're just not as flashy as the barbarian's magic effects. As for the dual-crossbow, it seems that people either love or hate it. And you know what? I think that's a more successful class than one that everyone's indifferent towards.

Besides, demon hunters are cunning as fuck and certainly have a lot of dexterity (in the literal sense). I like that you brought up the barbarian; sure they have magic effects on their moves, but do you think those muscles are just for show? The barbarians obviously have their own significant bodily strength (imagine a witch doctor using whirlwind - does it aesthetically work?), so it's only fair to excuse the demon hunters for having such a tricky combat setup. I think dual crossbows are only a testament to how clever and cunning the demon hunters are, which pretty much the main idea about them. So yeah, dual crossbow. It works.