Against the Bengals on Sunday, the split personality of a team not ready for prime time was clear for all to see. As anyone knows who remembers the Pittsburgh Steelers in the years preceding their first Super Bowl win, when an NFL team is several bricks shy of a load, it sometimes manages to conceal its flaws for a game here and there. But over the course of a grueling, 17-game season, the team’s true nature invariably emerges, particularly when facing quality opponents. In their Sunday matchup with the Cincinnati Bengals, the Bad Steelers actors showed up at the worst…