I saw this on the game's site, developer tips:
To get out of a Submission, the important thing to remember this year is to do something we on the team call "Clean Shines." Smooth, clean shining where you constantly touch the edge of the Right Stick/Right Analog is better than frantic shining where you jump from Stick/Analog surface to surface. And in general, Clean Shines are much more important than fast Shines (although the faster the Clean Shine, the better). A good rule of thumb to go by is that if you can hear your Shine, you're doing it wrong!
To improve your chances of successfully completing a Submission, all the old rules apply: make sure you're in a good advantaged position – it's easier to submit someone from Mount than it is from Open Guard – and make sure to take advantage of situation in which your opponent has low Energy (that's Energy, not Stamina, although sometimes by virtue of your opponent having low Stamina, it's easier for them to have low Energy). The only new wrinkle we've added this year is that it's also much easier to submit an opponent once they're Rocked.
Beyond that, Clean Shines is the only other tip I can offer.