I think EM's are very good to have in a FG farmer. They double your reward so they can prolly get away with a smaller winning % and more time to play them as the reward is worth it, but not too much of both.
So can we try and shoot for a win %? Try and make sure a FG farming deck can hit that %?
I would like to say that I started farming False gods without upgrades but my winning % was bad. After 2 upgrades it got easy.
If you have seen my false god farming deck it would be very close to that. Sundails, D shields, hourglasses, time pendulums, quint, and everything yu needs to have your win condition to go off, ie Fallen elf and monsters you can change, firefly swarm, ect...
Then a eternity so you can not deck out unless you have it at the bottom.