This is true and false at the same time. Sprint is the problem. Do not use the Sprint button, and the game plays like a dream. The pursuit of the LBs is fine, the problem is with the two high safeties who chase the wrong hip WHILE HOLDING SPRINT. Their pursuit is perfect if you are not using sprint. This problem was also the case in Madden 10 on the 360, and EA talked about that during the making of Madden 11. The Sprint button is a hold over from the SNES game that players love but "breaks the game".
Pressing sprint overrides your acceleration rating and you player instantly reached 100% of their maximum speed. Sprint also ignores your stamina rating and allows you to maintain that 100% speed. The developers also said that, in order to compensate for players suddenly pressing sprint, they had to add code for instant block shedding and how it made pursuit angle a challenge - especially as they continued to improve game play and running controls.
"But without sprint, speed doesn't matter as much!" is something I have heard over the years. Wrong. I matters more. Now you NEED guys like Jamaal Charles, Chris Johnson, Jahvid Best, and Darren McFadden. Guys who have 95+ speed (and who all are in NCAA 08). You also need your blockers, good scheme and timing with your play calling.
In my custom sliders, I am messing with RB Ability & run blocking for the user vs the CPU block shedding and tackle sliders to make a very satisfying running experience. The right thumb stick is the "Highlight Stick", which I go in and practice all kinds of moves and when to use them - to see if I am too early, too late or just right. Without using sprint, you can also feel your runner's natural agility and change of direction.
The AI doesn't use sprint, unless the user presses sprint. it is literally an arcade style feature that players love. EA tried to remove it forever in Madden 11 and players HATED them for it, so they brought it back for Madden 12.
Just stop using it and see how much better your experience is. If you have never played without depending on sprint, then there will be an adjustment period, but trust me... it is worth it, and you will probably also want to adjust your blocking vs block shedding sliders. Far too many players are accustomed to just out running their blocks around the edge to the sideline and call it a day. Far too few players call a pitch/toss play, allow the pulling linemen get out in front and create an alley for you to cut through. The purpose of the toss/pitch/sweep is NOT to get to the sideline, but - as Vince Lombardi taught - "Get a seal here! Get a seal there, and run it down the alley!" Some plays do set up where you do take it all the way to the sideline, but you get a feel for when that happens instead of just forcing it.