James Hunt is, to me, the same as if Eddie Irvine had won the world championship in 1999 after Schumi had his leg break at Silverstone. A decent driver but not world champion material, who benefited from a superior driver's massive misfortune.
For me, Hunt doesn't necessarily come into the classification of over-rated, not because he was better than you suggest,
but, because his calibre was never at the highest level. He may be over-rated by some, but, like many other drivers might not be over-rated because he hit the level of the expectations.
He won the championship in '76, not because he was the best driver,
but, because of the accident to Lauda. Even without the politics of '76, if Lauda had just not started the Nurburgring race, he would have been champion.
Hunt was always seen as a playboy, who on his day, could compete with the best in the world - he was certainly faster than most, but was he ever really touted as a Jim Clark.