Yeah I'm sure many people would find this useful, but it shouldn't be game breaking. Knowing which deck you are going to face is a huge advantage... perhaps somewhere down the road each false god could have several decks? But right now any reusable prediction shouldn't really tell you any more than "You will fight god A, B, C, or D."
It bothers me, though, that while this sounds like it would encourage people to go build new kinds of decks it actually wouldn't. Against the false gods unupgraded cards tend to be useless, so it'd still be best for most FG farmers to just stick to rainbows, occasionaly changing a card or two based on the prediction.