Ok, I figured this out by trying to tame a Amethyst shale spider. The warcraft pets battle tab is off when it comes to health, but not necessarily the other stats, sword and arrow. When you tame a pet the health will also jump, this is different then it was in beta, that I can recall. So for help determining rarity always check the sword and arrow stats, but even those will bounce about. They seem more reliable then looking at the health. I hope this helps other people.