I created two nations and teleported the prophets to an unconnected island of 4 provinces. The prophets did not preach.
Prophet test:
Candles in 4-province island, results at turn:
Code:
Turn Dom10@start Dom5,25 temples
==== =========== ===============
3 1 1
4 2 2
5 2 2
6 2 2
7 3 3
8 2 2
9 2 2
10 2 2
...
20 4 3
...
30 7 6
...
40 8 6
But, at 40 turns, 4 temples had been lost to random events, so it was actually dom5, 21 temples. It's not a 2-to-1 advantage in any case.
I then tested teleporting the Gods into the island instead of the prophets:
God test:
Candles in 4-province island, results at turn:
Code:
Turn Dom10@start Dom5,25 temples
==== =========== ===============
13 1 1
14 4 2 (oops, 24 temples)
15 4 2 (back to 25 temples)
16 5 3
17 7 5
18 7 5
19 8 6
20 9 7
...
30 11 8
...
40 11 8
...
50 10 8
...
60 11 9
Start without the 25 temples:
Code:
Turn Dom10@start Dom5,1 temples
==== =========== ===============
9 2 1
10 3 1
11 4 0
12 5 0
13 7 0
14 9 1
15 10 0
16 12 0
17 13 0
...
20 18 0
...
30 36 0
Anyway, that's good enough evidence for me I think.
(I started Arco with a dom-5 god and Ermor dom-10, indies at 0, uncommon events, on the attached map.)