For the longest time, I felt like he was overrated. When most coaches take over a team for the first time they usually take over a bad team without much to work with. Tomlin took over a team that had just won a Super Bowl, had a young up-and-coming talented QB, and a very good defense lead by maybe one of the best defensive coordinators ever. I think he benefited from a lot of help that most coaches don't get when they first become HCs.
Last year, though, I have to give him credit. He took a team with Rudolph and Duck Hodges and nearly got them to the playoffs. That was a darn good coaching job.
Still, though, I would say certainly at least Belichick and Payton are better.