>Sure that volatility seems pretty tolerable if my national currency plunges 30% overnight

I feel like that addresses the Ruble.

>but that’s a pretty unusual thing to happen.

Is the larger point. If you can magic 8 ball your country's future with all certainty, then yes, it is a good idea. Otherwise it's just speculative investment with your actual savings?

Yes? Just look at a chart of conversion rates between the two to USD over the past 5 years.