The Dragons no longer require the religious holy city (the first of them to be built causes the city that build it to become the holy city) and they both start with evangelism, so any city they conquer will gain the religion. Also, the spread rate has been increased.
I never really noticed it causing any problems before. It is probably stronger this way (although the negative side effects need to be increased more) since you can choose where to put the holy city and both dragons can be built.
I still think that the religion should be introduced at the appearance of Acheron, but the holy cities should be assigned later at the creation of Abashi/Eurabatres.