Warrior Armor bugged?Follow

I'm a bit confused on armor. I'm a level 14 Tauren warrior with an AC of 951. This provides, according to the tool tip, 38.1% damage reduction from a level 14 mob.

I was under the impression that, for a level 12 mob, the reduction would be greater.

I attacked a level 12 PlainStrider. It consistently hit me for 13dmg.

I then took off all my armor and I was left with a base AC of 50. I attacked another level 12 PlainStrider. It hit consistently for 17 dmg.

Now, 17 * 38.1% = 6.477 (the amount of protection I should expect if my AC is 951)

17 - 6.477 = 10.523 (the amount of damage I should normally receive at an AC of 951 from this mob)

It appears that my AC of 951, against a level 12 mob, isn't providing even the 38.1% protection. It's actually only providing 23.53% protection against a mob 2 levels below me.

Granted this is one sample, but does this seem like a bug, bad math, or am I missing something?

I tried to post this on WoW as well so that blue could reply. . .but their login server is down (again).