The only thing I am unsure of but I know is accurate for healing. Is the buffs are only active for current effects. For example if I used Divine Seal on WHM it buffed any HoT's I had applied and even if I refreshed a Regen or Medica II before Divine Seal wore off they lost they lost the potency boost when it was worn off. So in the reddit linked above it was discussing the 5% on Demolish. which would only be missing for 1-2 GCD which would be like 5 potency. I would need to do some testing with it but healing was a lot easier to notice.