Pot Helmet Interaction: Bug or Intentional?

Was playing Houndstone versus a fighting deck with Pot Helmet equipped, after taking damage, only 30 less damage was dealt. The wording of the card "This Pokemon takes 30 less damage after applying weakness and resistance" made me think and additional 30 less damage would get dealt after applying Houndstone's -30 fighting resistance. Does this wording imply that Pot Helmet is a redundant effect if you are already taking 30 less damage from an attack? Very confusing and a bit unintuitive if that is the case.