Yes, platitude aside, good play by the MLB is important, not as critical as it was 20 years ago but still important. But on 3rd and very long, the most critical elements to stopping a first-down completion are a pass rush, good coverage by the CBs, and safeties ready to protect the sticks. I think people may tend to underestimate the critical importance of PRC, especially for the MLB. It's the attribute I upgrade first and fastest, and I don't have complaints about my MLB biting on play action on 3rd and very long.