Not just difficult to beat when they are at home with a large lead. Up to last night a better word was IMPOSSIBLE to beat. I read on PFT that their record at home with a 14 pt lead was 220-0-2. So yeah, that was a once in a lifetime event.
BTW- For all the fun we like to make about Mike Tomlin, he isn't a "bad" HC. You don't have the kind of success the steelers have had and be a "bad" HC. He simply doesn't fare well when you are comparing him to BB and the Pats. But relative to the rest of the NFL universe, he's done pretty well.
I think of him as a big picture guy who has run a good program for a lot of years. He'd improve a number of franchises if he led their teams. What he isn't is a premier x's and O's guy. Instead he' one who lets his coordinators run the game.
On the other hand, if I were a Steeler fan, I'd be angry that he's wasting perhaps one of the best rosters in the league the past few years without coming close to getting past the Pats.
Top 8 QB, top 3 receiving corps, great OL, solid TE's, and a good/great running attack, and
a decent defense full of #1 picks. Not a lot to show for all that talent. It must be horrendous for them to keep losing to a team that (to them) consists of Brady, Gronk, and 51 guys who most of their fans have never heard of.
No wonder they think the Pats cheat.
So no, Tomlin isn't a bad coach, he just looks that way when you compare him to the guy we have seen these last 19 years.