Haslett was carried by Mike McCarthy and he got many years of rope. He was HC for 6 years and only had one other winning season with 9 wins. It took five years of frustration and mediocrity to fire him. They didn't even fire him when they found out he got a Saintsation pregnant. They fired Mueller for paying her off to stay quite with Benson's money without permission.
Maybe you could argue Haslett was a bit better than DA, but he got 6 years and DA is at most getting 4 and I think likely only 3. That is unless he somehow turns it around. But DA only has one fewer winning season than Haslett and has 4 fewer years at this point. If Haslett is better it's not by much.