Thats pretty good, but I just thought I'd offer some suggestions to the set:
Switch substitute for protect:
you never know if the opponent is going to set up, or they intend to hit you with that wasted chunk of hp away,the orbs will only bring you down quicker. True, you are slower when you set up the sub, but otherwise it's too great a risk to take.
Toxic Orb: Now this contradicts my previous statement, however the conclusion must be made that guts users or quickfeet users arn't gonna be lasting long. With that said, its much better to give a status that wont cut your attack, as high as ursarings attack is
Quick Feet instead of guts: Now ursaring has a very respectable attack stat, paired with guts, making it deadly. However, if you use quick feet, and give it a stronger nature in attack, you'll find a faster ursaring, by sacrificing only a few attack ev's, can go a long way.
With that all said however, I enjoy these two-step last resort combos, and would love to hear how it works; possible damage-calcs would be great!
~Aero