I'm not all that familiar with the setting beyond what I've read in the RPG books.
Is there a reason (other than Pure Faith came out in a sourcebook which followed the core book) that the Pure Faith talent is not available to clerics (or even other extremly pious characters)?
Would that break the setting in some way? Would it steal the "soul" of the Sisters of Battle?
If you were to make it available to Clerics, would you allow them to have the later talents as well? Should it cost more? How much?
) figure that they can test purity by burning suspected heretics with something like the "Flames of Faith" Talent? Might this encourage a pyromaniacal hysteria with everyone running around setting each other on fire on flimsy charges of heresy?