Religious Discipline might be the most unbalanced Civic in the game. Most notably it synergizes with Altar of Luonnotar, creating a power loop. It allows an unlimited number of Hammer producing Priests, which in turn spawn more Great Priests to build further Altar Stages and quickly climb the religious tech ladder.
This loop has been documented, and by itself it's a powerful strategy. However, the loop alone isn't what makes the civic unbalancing; the real kicker is that Religious Discipline gives
+10% in all cities. This is the same base
bonus that the Scholarship civic provides! (without the unlimited sages and free
per specialist, of course).
For both flavor and game balance, Religious Discipline should have the opposite effect on research. I suggest a -20%
penalty to the civic; I would suggest an even harsher penalty, but I think that might drive the unrest in this forum a little too high.