There were lots of ways the offense failed in 2011, which was the general reason why offensive coordinator Bruce Arians was let go, and replaced by Todd Haley.
Through two games, the most glaring piece of the Steelers offense is the rough state of the running game. What is getting lost in the shuffle is the performance of Roethlisberger, and how he may be, through the small sample size of two weeks, be performing at an MVP level.
According to Advanced Football Stats, a site tracking statistics deeper than wins, losses and yards per attempt, Roethlisberger leads the NFL in Win Probability Added (WPA). It's based off a parent stat, Win Probability (WP), that measures plays contextually, and gives a percentage of probability a team wins given the situation (down, distance, score, field position, etc.). The result of the ensuing play, and the variation of the following play's WP is WPA.
Simply put, through two games, no quarterback has done more than Roethlisberger to improve his team's chances of winning on a play-by-play basis.
Roethlisberger has a WPA of .93, leading Atlanta QB Matt Ryan, who has .83.
The main thing holding Roethlisberger back, despite his league-leading status in this department, was a game-ending interception at Denver.
His main advantage has been his success on third downs. Roethlisberger, through two games, is 19-for-25 with 251 yards and three touchdowns on third down, and an amazing 11-for-14 with 203 yards and a touchdown on 3rd-and-long (six or more yards).
The general thought on the structure the team wanted for Roethlisberger under Haley was less deeper passes and more quick throws, hoping to protect Roethlisberger while using the quickness and speed of their talented receiving group. While he appears to be doing that, it hasn't been by much so far. Through two games, Roethlisberger's deep pass attempts percentage (defined as passes to receivers who are more than 15 yards from the line of scrimmage) is 21.1, 13th highest in the league. In 2011, it was 22.8, 11th highest in the league.
Translation, this offense through two games is pretty much as vertical as it was last year. Roethlisberger is just playing better.
Through two games, he's 46-for-71 with 520 yards, four touchdowns and one interception.