Not sure how accurate that is but according to this eqemu npc scaling chart lvl52 named has 32 MR. Outside of mobs with abnormally high MR it would seem you could bottom out resists with tash on almost anything you can boltran. We don't know if the NPC resist floor is 0 or if going under 0 provides additional benefits to charm.
https://docs.eqemu.io/server/npc/npc-scaling/