Considering this point of view, it is valid only for FCs housing since it is a shared housing.
Interiors are instancied already.
Having the feeling to be in a dormitory city is not exactly what I call a neighborood feeling. This said by someone who owned two mansions. I don't miss the neighborood, I miss the gardening and the space I had.
Even thought they will open Ishgard one day or another, I'm not sure to take any house since I would prefer an instancied housing I'm sure to keep and where I can put all the collections I can already craft rather than have a fake show off effect, a dormitory city feeling and the risk to lose everything I crafted.