The Demon Hunter was the fifth and final class to be revealed for Diablo III at Blizzcon 2010, despite being the first character Blizzard began work on. Like all of the character classes in Diablo III, the Demon Hunter has gone through numerous changes.
The original concept of the Demon Hunter involved the character being an actual demon. This original concept (seen in the image below) was ruled out by the team at Blizzard on the grounds that it ran against the overarching theme of the Diablo franchise - that of humanity fighting against demons. The next stage of the design concept for the character class proposed a human possessed by demonic features (to be specific, a demonic arm). Again, though, the concept was ultimately abandoned - not only did it continue to feel at odds with the Diablo storyline, it also resulted in a bulkier, slower character class with a new focus on melee combat; all things that clashed with the original concept for the Demon Hunter class.
At this point the 'demonic' Demon Hunter concept was scrapped entirely and the development team began again from scratch. The final version of the Demon Hunter class is completely human, with a sleek, sexy look, and a dark past that fuels her desire for retribution against evil.
Demon Hunter design progression.
This final design is much more reminscent of fictional medieval bounty hunters, and clearly takes strong inspiration from characters like Van Helsing, as Jay Wilson noted in an interview for the 2010 Blizzcon Program:
"With the demon hunter we found inspiration in characters like Van Helsing, Boba Fett, and even MacGyver. The demon hunter is very focused on conventional, man-made weaponry and gadgets. She dual-wields crossbows, and where one class might conjure a magical fireball, the demon hunter would buy a device in the lower markets of Caldeum that would allow her to trap the essence of a demon and then release that essence in an explosive blast, not unlike a hand grenade. She has no qualms about using her enemies against themselves, dabbling in dark magic, and generally doing whatever it takes to destroy demons wherever they live."
Female Demon Hunter armour progression.
As with all of the character classes in Diablo III, the Demon Hunter has a resource system unique to itself - in this case a dual resource system known as Hatred and Discipline. Hatred (the red portion of the orb in the image below) is the resource used for offensive attacks, which regenerates quickly. Discipline - the blue half of the orb - is the resource used for the Demon Hunter's defensive maneuvers, and also some of her traps. As Jason Bender, Senior Designer for Diablo III, explained in an interview with Gameplanet:
"We’ve split their kit into the idea of discipline – prepared, deliberate, precise – a character who builds his traps ahead of time and knows every weakness of his enemy and exactly what he has to do to take it out. Then there’s hatred, this almost blind drive – they can’t stop themselves from getting involved which means they’re probably angry at themselves for having that taint and it makes it worse. So they’re obsessed in that way. Their skills match that: They have some very aggressive skills that come out of that hatred school, and they have discipline skills, that deliberate, intentional preparedness."