I remember frost mage also being at the top next to BM hunter in those stats for a long time, but you wouldn’t say mage was in need of any defensive buffs.
Shadow has a lot of passive healing and even gets a boosted fortitude buff, and a 10% hp shield. I’m gonna bet that just like balance and bear form, a lot of you guys refuse to flash heal yourself for the DR benefit or press power word shield. You can pretty much stack all those things with fade and basically have 0 cooldown.
After all, dying is better than losing a gcd pressing a defensive.