Talking of devaluations ....I'm sure I identified yet another example just recently.
I needed to sort a standalone o/w sector from HKG to BKK. Was about to use some Skywards for an EK award flight..... either 20K in J or 30K in F. Not wonderful, but not too bad.
Next time I looked (ie once my travel dates were sorted and I was ready to book) it was showing 27.5K and 37.5K respectively. That's just unreasonable for such a short sector.
In the end, I used some of my Avios for Royal Jordanian in J. Don't know how they'll stack up vs EK - but the timing suited me and it was a lot 'cheaper' points/miles-wise.