Immune to Pain doesn't reduce damage from melee attacks
The Immune to Pain talent does not reduce the damage the PC takes from melee attacks.
Tested with a 3 PV character fighting a goblin with 1-6 damage. On normal hits the goblin should have been able to do at most 2 damage (6 - 3 (PV) - 1 (Immune to Pain)). It was able to deal 3 damage on normal hits.