That is actually an interesting point. -20% defense would be a 14 percentage point improvement in the debuff from the RP trio. Undispellable just means that, if there is a cleanser on the team, they can’t remove the debuff. But RP is dispellable, so I assume it is also overwritable, both by a defense buff and (in this case) a lower defense down. The duration on the rabbits’ defense down is also 3 turns, versus 6 for RP, so I wonder if it also cuts the duration by overwriting RP. Good questions.
I’ll try to pay attention to this going forward, as I use both Grimm and Gormek on my main team. So far, none of the rabbits has fired, as I’m still in the early stages. Hope to have an answer relatively soon.