Difference is, that '72 Dolphins team had the #1 offense in both yards and scoring, AND the #1 defense in both yards and scoring. They had 3 shutouts, gave up 20 points or more just 3 times, including playoffs, and beat opponents by an average score of 27.5 to 12.2. And that wasn't with a high powered passing attack. That was running the ball 354 times more than they threw it.
Even if it was an "easy" schedule, they dominated it. Sure they had some close games with some mediocre teams, but it is the NFL and it ain't easy winning every single game. The Texans are winning games on their "easy" schedule, but they are far from dominating.
There were also 6 fewer teams playing 2 fewer games. Only 12 teams with winning records then as opposed to 17 last year.
You wanna tell me that if the 2011 Giants, who gave up more points than they scored that season, can win a SB then why not the Texans, I'm with you. But don't compare them to '72 Dolphins. That team was one of the greats.