I think Defender of the Faith is overpowered or the wide empire alternatives like Faith of the Masses/Jesuit are underpowered. Probably the latter because FotM/Jesuit really aren't impressive. DotF has by far the strongest yields that come in the most timely manner as well as likely the strongest secondary effect which is 30% CS in your own lands. Now that it has it's 3
2
from Wall, Castle, Arsenal back (was 1 faith for a time), it seems even better compared to Culture belief in comparison. Faith of the Masses, at the very same point you get +6C +4F from DoTF (early medieval) can only give 2 bonus Culture from Amphitheatre and another 2 from Opera House an entire era and half later, as well as some Happiness and buildings that cost quite a bit of Faith. FOTM/JE faith costs seem very high unless I'm very wide wih Faith and either someone like Ethiopia, or sporting 1-2 religious buildings with good Faith and Fealty and even then they seem high, especially after they scale. This makes them too niche for a reformation belief, unless their niche is being inferior to DOTF. I don't think I'd pick FOTM or JE unless DotF was taken.
I don't understand what DoTF is meant to need all this faith for, it's not the belief that will be spending thousands upon thousands of it on buildings.