OK, so a bit more testoing, i think 10.4.1 has done something to this, in the area of limitations... i just did a test where i:
1. logged into orion as an unrestricted user
2. removed the limitation on the view in question
3. previewed it, and the hardware overview appears fine, but for the whole estate rather that the subset i need
4. logged on as a restricted user, tested that same view, and now the view shows "Data is not available"
so not sure what it is,m but it looks like the view has changed to ONLY work on unrestructed views now... as it refers to the entire estate...