Ancient Tongue, Madness difficulty, the Pharaoh Dog King's passive Alchemy says "Clears A random debuff from an ally and heals all allies based on their HP every round"
Finally down to two, and then one PDK, they cleared all debuffs (4+) every turn, not a single debuff.
Didn't try any other difficulties.
This is either broken or the description is incorrect. "A" is singular, not plural.