Well, when you consider the fact that we probably lost ~3 or more games due to poor coaching decisions, and a few more games because Haden was out causing our CBs to get raped, it's not that big of a stretch. The NFL is the easiest league to make a quick turnaround in.
You guys are overestimating how much they lost. They still had the number one defense numbers-wise in the league. Harrison was hardly effective and LaMarr Woodley had a bad year. Polamalu can't stay healthy, the CBs suck, but still had a great defense. Unless Ben Roethlisberger gets hurt, they are still good for 8 wins, at least. As for the Bengals comparison, Andy Dalton showed more as a rookie than Brandon Weeden did, that's for sure. He made the Pro Bowl, as did Andrew Luck and RGIII, in their rookie seasons. If Ben Roethlisberger goes down, and the Steelers have to rely on Gradkowski or Landry Jones for an extended time, then yes, they would be in danger. The Browns and Steelers have the same exact schedule, save for the Browns playing Kansas City and Jacksonville, while the Steelers play Oakland and Tennessee.
In NBA terms, the Steelers are like the Celtics. They are a good team that has won recent titles, but everyone is wondering how much they have left and how long in the tooth their players are.
The Patriots are the Spurs. They are a veteran team that has the best coach in the league. The draft doesn't matter too much to them. They won titles in the early 2000s, but cannot get back over the hump in recent years, for some reason.
The Ravens are the Mavericks, a constant threat, broke through once, but show no signs of winning another one soon. Like the Mavericks, the Ravens lost a ton of players in the offseason right after their title.
The Bengals are the Clippers. Historically bad team that hit on a few moves. Had a fickle fanbase that came back upon winning. Will make playoffs semi-consistently, but will likely never win one.
Cowboys are the Knicks. Haven't done anything in YEARS, but fans will always talk about "the good old days".
Browns are the Timberwolves, haven't made the playoffs in years and have had frequent regime changes. Both think they are on the right track, though.