How were your non poser content libraries set up? Were they separate runtimes? If so the problem was that when you installed poser 11.2 you didn't select the option of retaining your preferences. The installation of poser 11.2 would not have deleted any runtimes, they would still be on your hard drive, you would just have to get poser to see them using the add library function.

Manually installing DAZ content has always had that problem, it is due to the way DAZ packs their product. You have to install manually by unzipping the package and merging the runtime folder with the runtime folder of the library in which you wish them to appear.

As far as using the DIM, by default this adds the content to a folder called My DAZ 3D library. I rarely use the DIM, but when I do I just let it install to its default and I have this library as a library which I have added to poser.

There is nothing underhand going on with poser 11.2 not allowing you to use DAZ content or making it difficult. Since the update I still use all my DAZ content and install new DAZ content exactly the same as before, I have all my previous libraries and have no problems.