I filed the bug reports in Mantis some 2 years ago shortly after the DSON importer was released.

A half year later most of them had not even been acknowledged and then access to mantis was removed and all issues were gone.

With each subsequent release I tried the DSON importer again and still my main problem remains: If you have a set of morph sets installed and you load multiple figures with clothing and hair, the UI will start to get slow and finally freeze up Poser. At that point you can only kill the app and lose your work what you have not saved. That is the main reason why it is unusable for me

That sounds as if you made the report just before DAZ moved to handling bug reports through technical Support. I think the Mantis tickets ar still there, but make a new report (via the Zendesk Contact Us) and tell them Bruce sicced you on to them.