Are there concrete class roles in Diablo 3?

In some games, notably MMORPGs like World of Warcraft, each character build has a specific role in PvE situations like dungeons and raids.

The developers have said that—at higher difficulties—players in a party can spend up to an hour wiping to a single boss. This made me wonder if there will be concrete class roles like there are in other RPGs; for example, a barbarian using a specific set of abilities or gear would necessarily have to take the role of the “tank”.

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    Also, is there any room for Crazy/Viable Builds ?
    This Last question is answered on the Video posted in the answer bellow.

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