Ursaring's problems:
- Lacking bulk- 90 / 75 / 75 isn't really making the cut when you have no resistances to fall back on.
- Lacking Speed. 55 base Speed is awful, and even with Quick Feet, you still fail to outspeed: Terrakion, Virizion, Lati@s, anything Scarfed, Thundurus, Tornadus, Jolteon, etc. You're not sweeping anything any time soon with Quick Feet.
- Steels shit on it. It can't really deal with most of the Steel-types in OU (other than Ferrothorn) because most of them are neutral to Fighting (Bronzong, Metagross, Jirachi, Forretress, Skarmory). In addition, all of them except Forretress and Ferrothorn outspeed it, which hurts.
- It's outclassed. As a Guts sweeper, Conkeldurr wins. As a bulky normal-type attacker, Bouffalant wins. As a "fast" sweeper, pretty much everything wins. Why should I use Swords Dance Ursaring with Quick Feet when I can use Swords Dance Terrakion which is faster, stronger, has better STABs, has better defenses, and has ACTUAL resistances, and doesn't have to get Toxiced to do it.