Ephara, God of the Polis
I think this may be a sleeper card, in that it doesn't look like much, but it will find some weird way to be awesome in some format. White and blue do have the most flash creatures, so there's definitely the potential for something. Still, I can't shake the feeling that maybe this effect should be blue/green instead so that token decks can get a lot more use out of it.
Pros: First creature per turn trips
Cons: Not in most abusable colour combo
Karametra, God of Harvests
Hi there, new EDH superstar! Given that cards like Admonition Angel and Avenger of Zendikar are already staples of some white and green decks respectfully, this card brings both worlds together in what I envision to be a scary, fast deck (think a Kamahl, Fist of Krosa EDH, but with a lot more removal). Outside of EDH, I can't see this being played.
Pros: EDH superstar
Cons: Ignorable out EDH
Mogis, God of Slaughter
This card is kind of the opposite of Karametra, God of Harvests. I can see this being played everywhere except EDH (as a general at least). It formats like Standard and Modern, this card will definitely keep the pressure on your opponents by making them sack a dude or lose 10% of their starting life each turn, but in slower formats like EDH, that may not matter as much (especially since it's only dealing 5% of starting life there). I view this card the same way I see Desecration Demon, except that no matter what they choose, they're getting punched in the face.
Pros: Non-EDH superstar
Cons: Weak in EDH
Phenax, God of Deception
This is the weakest god in the set without a doubt. I can see it sort of working in a causal or EDH Wall-deck, but outside of that it's really weak. Milling is not as strong or as viable in tournament play as WotC seems to continually think it is. It's very flavourful, but not very impressive in-game.
Pros: Flavourful, good in a Wall-deck
Cons: Not competitive, only good in a Wall-deck
Xenagos, God of Revels
Basically, take what I said about Mogis, God of Slaughter, put it here, only replace the part about sacking a dude with "forcing your opponent to sack a dude or die". I see this card like the new Hellrider, that thing you don't really think will be a problem until you play against it once or twice, wherein afterwards you live in fear of it for the rest of your life. The only issue I have with it is that is does come in a little too late for my liking. I would have rather liked to see it cost 2RG.
Pros: Rush down champion
Cons: A smidge too expensive