Milling five cards can be awfully close to drawing that many cards in the right deck
As nice as +2/+2 buffs may be, the real draw of Howling Moon is its ability to create tokens
All you need is a permanent marker and a Magic card you dont mind defacing
Any individual god can be the centerpiece of a deck built around their strengths, but Wizards has also carefully orchestrated things so there are incentives to play an all-gods deck in non-rotating formats like Commander
Toss in excellent support from new cards like Mirrormind Crown and Mutagen Man, Living Ooze, and you have a great card
The answer, as it turns out, is to make black absurdly powerful in Avatar: The Last Airbender to compensate for the fact that it doesnt have a designated element and form of bending, like white (airbending), blue (waterbending), red (firebending), and green (earthbending)