"As an artist, game developer (not affiliated with Blizzard) and long-time fan of the Diablo series, I've found the new art direction to be undesirable in many regards and hope the following points best clarify why I'm complaining about an unfinished product atop my virtual soapbox:
* IP Ambiguity: Blizzard has rocketed to the top of the success ladder with its three main Intellectual Properties: Warcraft, Starcraft & Diablo. These three franchises can be categorized, in terms of genre as: High Fantasy, Sci-Fi/Fantasy & Dark/Gothic Fantasy, respectively. The categories help customers clearly identify the three IPs. This new art direction (seen in Diablo III's public announcement) blurs the lines between two of Blizzard's IPs. "Is that a Troll Witch Doctor I'm looking at or something from Diablo?" By doing this, the IPs become harder to discern and the end result is a watered down version attempting to accommodate both the demographics... akin to a jack-of-all-trades, master of nothing scenario.
* Fanbase Alienation: The Diablo series has always been in a dark and dreary setting that instills a foreboding sense of hopelessness and futility. This couldn't be any more reinforced by the ironic conclusion of the first game: the hero defeats the devil but willingly sacrifices his/herself to contain the unstoppable evil. The powers of these beings is something much bigger than any of us, the heroes or the mortal world. By making things cartoonish and less 'gritty' and somberly realistic, the oppressive dread is no longer felt.
* Artistic Discontinuity: In metaphoric art terms, Warcraft is a colourful oil painting: the textures contain palettes of vibrant hues and hard lines define soft shapes. Diablo, on the other hand, gives the impression of being more of a charcoal illustration: realistic and heavily influenced by black and muted hues. Magic is still colourful but doesn't over-power a scene with a conflagration of blues, green, reds and purples. Color, when used sparingly, can direct someone's eyes to an intended point of interest. When over-used, it makes the eyes tired and desensitized. On the opposite side of the that, under-use can also yield bad consequences. The point is, the world of Diablo isn't a colorful place and when vibrancy is introduced into a macabre setting, it feels more surreal than terrifying."