The scenarios I posted were to be interpreted separately.
Nothing is immune to an ice-type Rapid Spin~... But that wouldn't make sense since Rapid Spin is already useful.
It's mostly the priority that bothers me. And the fact that it sometimes has 60 base power.If Refrigerate only boosts Normal-type moves, that's dumb. And also makes Return more useful. In the case it doesn't, you can't ignore that 18 BP. It'l be important t' secure a KO on a specific Poke with a specific EV spread, guaranteed. The only question is, will that Poke be a threat in Amaura's tier and thus make my situational argument at all viable?
Return versus Avalanche in this scenario is akin to Rock Slide versus Stone Edge. The extra power WILL be work the downside in certain situations. It's only a matter of whether or not said situations will crop up often.
Stone Edge doesn't have negative priority and hits at full power 100% of the time. The argument between it and Rock Slide is trading power for accuracy (and technically PP). With Avalanche and Body Slam/Return/Double Edge, it's not a matter of accuracy at all.