Some people made tests. I also made tests that confirm what I read. Here is the situation :
1) To spread villagers on different temples have no effect.
This came as unexpected.
But the most unexpected thing is this :
2) Four villagers gather favor slower than 3. 5 villagers gather favor exactly as fast as three. So never put 4 or 5 villagers at your temple, 3 is enough. After 5, the situation become more logical, the gathering speed increase with the number of vils, roughly linearly which means that 10 vils are twice as fast as 5 and so on....
So, my advice is have 3 vils at your temple, the flow of favor will be nice. If you need favor in a hurry, put 10 or more until it gets to 100 than move them to something else.... No use to pray when the favor cap is reached...
The only usefulness of having more than one temple is not related with favor gathering but with forward building. Some myths units are slow (cyclops, hydras, ...) you don't want them to spend their time walking between your base and the opponent's town. One temple at home to gather favor and research myth techs and one forward temple for MUs production seem to be OK. As the location of the fights move across the map, more temples might be needed for MU production. Also, 2 temples produce MUs twice as fast as one, so if you use MUs a lot, think about it. If you only make a few of them as support units, then 1 production temple might be enough. In addition to your home temple.