Back to the original post... I agree with you.
These stats (92% pass when in gun and 85% run when under center) combined with the fact they were among the lowest play action teams in the league AND they never threw the ball in the middle of the field made them incredibily predictable. There are defensive assistant coaches in the league making 6 or 7 figure salaries who spend hours each day watching film to find tendencies and scout their opponents. I'm just some dude who watches the Steelers every week sitting on my couch and I could predict their play calls 75% of the time or more the last 2-3 years. If I can do that, then you know their Steelers opponents could. The opposing LBs were always coming downhill on run plays b/c they knew it was coming and had no fear of being beat by play action or a pass over the middle. The opposing D-line could tee off on pass rush when the Steelers were in gun. Etc.
Frankly Najee, Warren, Friermuth, Pickens, Johnson, Pickett, Chuks, etc. all had reason to be frustrated. Everyone of them probably were asking their agent to get them out of Pittsburgh. They all looked worse than they are and couldn't excel becasue they were rarely put in a position to win by their coaches. These guys were always playing with one arm tied behind their back.
Tomlin was complicit in this because he should have seen it and addressed it sooner. Every NFL team employs assistants whose job is to scout their own team. They had to know how predictable they were.
Given that they've hovered around .500 and been in the playoffs or in contention for the playoffs the last 3 years with arguably the worst offense in the league... it won't take that much improvement on offense for them to be a legitimate contender. The offense doesn't have to be good, just not suck.