From Diablo Wiki
"Barblo" is a joking portmanteau created by merging "Barbarian" with "Diablo," referring to the game title. It alludes to the very powerful (most would argue overpowered) state of the Barbarian class, especially as evidenced by the Spin2Win build that is the fastest moving and killing build in the game.
Adding fuel to the Barbarian resentment is the fact that other classes have had their own overpowered builds, but those were nerfed in various patches while the Barbarian's has not been touched.
Further arguments of favoritism stem from the Barbarian being the only returning class from Diablo 2, the first class showcased when the game debuted, and former Game Director Jay Wilson's repeated confirmations that the Barbarian is his favorite class in the game.
Player attitudes towards the "Barblo" state of affairs vary. There's little debate that the Barbarian class has the strongest build, at least for PvE, but opinions differ on whether the Barbarian needs to be nerfed, if other classes need to be buffed, or both.
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