I'm pretty sure crits ignore lowered defense. Although if I'm wrong please correct me.
Also I don't have poison fang on my team I just wanted to point it out.
I believe the exact way that it works is critical hits ignore any stat changes that would lower your damage (so it ignores your atk drops and the opponent's def boosts).
I like how ice types actually have a defensive niche being immune to freeze, finally. And since every freeze move other than the 1/3 chance on Tri Attack/Nature power is ice typed, they are the best switchins. Water types with Scald work too, but the scald is obviously predictable.
Also, this looks fun:
Ursaring @ Toxic Orb
4 HP/252 Atk/252 Spe
Adamant/Jolly nature
Ability: Quick Feet
- Headbutt/Facade
- Crunch/Ice Punch
- Rest
- Snore/Sleep Talk
Basically, Toxic Orb activates Quick Feet, and then you have 418/458 speed depending on nature, 130 base attack, and stab crit Headbutt or Facade. Facade is twice as strong as Headbutt when poisoned, and Headbutt is for the flinch fun. Crunch hits ghosts super effective, while Ice Punch hits regularly and just freezes them. Rest stops Ursaring from being worn down too much, and you can burn the two sleep turns with Snore, since you're still under Quick Feet and Snore has a flinch chance. Sleep Talk prevents ghosts and scarfers from getting a free turn but you can get haxed by picking Rest.