Broadway sustained its worst sesh since the first frame of 2012, with overall box office tumbling more than $3.4 million in Week 40 (Feb. 27-March 4) and attendance down by nearly 25,000, despite the addition of two previewing productions.The bad B.O. mojo was spread pretty evenly among the 27 shows on the boards, with only “The Book of Mormon” ($1,493,754 — up 2% and setting yet another house record at the Eugene O’Neill) and just-shuttered “The Road to Mecca” ($250,244 — a 14% uptick in its final week) increasing their haul. If there was a silver lining, it was in previewing productions. The Philip Seymour Hoffman-toplined revival of Arthur Miller’s “Death of a Salesman” ($661,262 in seven perfs) cracked the top 10 list ahead of its March 15 opening, down only 4%. Tuners “Once” ($525,050) and “Jesus Christ Superstar” ($370,699 for four perfs) also opened strong. The overall Broadway cume was $16,890,525, an increase of almost $2 million against the same time last year, when 26 shows were running. Attendance stood at 192,998, or 75.7% capacity. The 19 musicals grossed $13,619,177 for 80.6% of the Broadway total, with attendance of 153,387 and an average paid admission of $88.79. The eight plays grossed $3,271,345 for 19.4% of the Broadway total, with attendance of 39,611 and an average paid admission of $82.59.