Repentia Mistress has no current purpose in the WD Dex
This is exactly what I thought. I made allot of suggestions on how to make her interesting. The fluff says that she is the only one who can grant a Repentia repentance if they have shown themselves worthy at the end of a battle, she is also responsible for pretty much everything in their lives. As she is so important to them this should be represented on the gaming table. One thing I did was that the unit could not use AoF if she died, another was bring back the WH codex rule that if she died the unit immediately makes a Holy Rage move towards the unit responsible for her death. She also carried some wargear like the grenades that made every model in the unit count as having frag grenades.
The question I wanted the gamer to ask themselves was do I keep her alive so she can provide all the bonuses to the unit or do I let her die so they can get the Holy Rage move towards the enemy, but if I do this they lose the ability to use AoFs, some of which were quite nice...