The problem with Inferno is simple: There are five difficulty levels, for five different classes.
Wizards have the most tools to negate the bars set forth in Inferno. They can avoid damage completely and have skills which allow them to make mistakes and still come out alive to continue to fight.
Demon Hunters deal an overwhelming amount of damage and can avoid damage if skilled enough. They do not have the ability to make mistakes though.
Witch Doctors have the advantage of some considerable burst and the natural advantage of being ranged, but can be overwhelmed easier than the above two classes if not played precisely.
Barbs and Monks take turns trying to scrape by enough gear to be able to do anything. This Inferno nerf was 100% required for anyone sane to play Inferno. It wasn't impossible, but we are talking about 10k armor/1000 resists and still struggling in Act IV for some people.
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The Cult of Personality.