Am I reading Red-Gold Mortality correctly?
Once it blocks or diminishes a single instance of healing, it simply stops working.
For example if an enemy cleric healed a wounded ally, and saw it blocked by obvious magic, then clearly saw said magic go away, all they'd have to do is try again? If it were me, I'd start using a 1-action loww-level heal to remove the effect followed by a 2-action high level heal to get the target to full health.
Or a troll may not gain Hit Points from regeneration in one round, but still would in the next round? (It also only blocks healing, this feat doesn't actually seem like it would allow you to kill the troll.)
Seems kinda weak and circumstantial. Do we really need additional restrictions and limitations over the 1 minute duration?