I don't know about faith points, they don't just have their sins forgiven for fighting. They are based on Flagellantism movement from the 13th century
http://en.wikipedia.org/wiki/Flagellant
It is a self imposed exile as much as anything.
I've play tested Repentia trying various rule combinations with them:
The three best options I have come up with is either drop the armour save for Feel No Pain and reduce their cost to between 6 to 9 pts.
Or
Drop the armour save for Feel No Pain and have it so they get to strike even if they were killed that turn. Pts 10-15
Or
Drop the armour save for Feel No Pain and have it so on the charge they strike in I order and subsequent attacks are at I1. Pts 10-15
No matter how you cut it, they need a massive points drop as no amount of buffing can be justified at their current rate.
I personally like the idea of merging options two and three for about 13-15 pts. (I believe even then it is still probably to high a cost for their use)
Then they'll finally start to match fluff.