Hmm, I really think my Decay would be a good FG (no offensive/sarcastic comments like "WTF, Light master made a Dark/Aether deck")
Now, about the bad Fractal usage.
IMO, this is a bad AI case which should be fix'd. Anyways, It has enough Aether towers to pull out a Fractal before the classic rainbow even gets a creature out.
Reasons this god is awesome:
1) Small rainbows will remain quantaless.
2) Big rainbows will be too slow.
3) It will laugh at quinted Oty.
4) It can still be defeated if you get it in the Oracle with a Jade Shield.
Now, about Neptune. No offense to the designer, but I REALLY don't find it to be such a good deck:
1) Air quanta is sooo wasted. In 2 turns you get all the quanta you need. After that, the mark is useless.
2) Not too much damage, Permafrost and SoG's kill it. And the most popular FG killer (Pupp's) both has both.
3) Pulv kills it.
4) Quinted Oty kills it.
So, vote for Decay