Depreciation of DA42s and DA40Ds is high for a different reason
Partly true I have no doubt.
However you can buy a 42 with a fixed price guarantee from Diamond for replacing the engines with the new diesels for a remarkable price.
Moreover Thielert seem to have resolved most of their issues, the prices of parts has fallen dramatically and perhaps a 40 or 42 with Thielerts is not such a bad buy.
However many of the 42s were sold to flying schools to replace ancient twins. Many have already upgraded their fleet and in the same way as Cirrus the ones keeping their bank managers happy with profits will be selling of their early 42s and replacing them and the ones not keeping the bank manager happy will be selling them because they need to.
It all adds up to a market with similarities across the fleet and elements unique to certain types - I suspect the uptake of Diamonds by schools has been far higher than the up take of Cirrus.