No inside information or anything but from seeing a lot of research guys have posted for me in the slider threads there is a huge disparity between M25 and the NFL. Not only M25, but probably most of our general perception of NFL averages.
If you have run 10 plays and have 60 yards you are the best offense in the NFL. (Broncos were at 6.3 last year). In Madden 60 yard drives are usually less than 5 plays even without a long ball. You get consistent pass plays of 10-25 yards. Most NFL passes are completed for less than 10 yards. So it's about getting these averages realistic.
So if Broncos lead the league with 450 yards per game with 60 minute quarters. In Madden's 20 minute games you should consider 150 yards (same avg) a stellar offensive performance. In M25 get 400 yards on 5 minute qtrs really wasn't hard to do at all. Should be damn near impossible.