I broke up the render items into two sets as an initial solution, made two resources of about 3.8GB, and it works. Just a bit more logic needed to handle when render counts fluctuate 0-max. 

I plan to experiment more with the 4GB limit when I have time. 

I believe (and @SoldierOfLight can correct me on this if I'm wrong) that the current way the memory manager works is that it requires contiguous physical memory for each committed resource. Obviously it's not always going to be as easy to find 4GB of contiguous physical memory even on a card with 8-12GB of VRAM, so once again the multiple-heap reserved resource approach will work around the problem.

For such massive resource, you may also want to look into using tiled resources, which gives a lot more flexibility on the mapping between virtual address space and physical pages of data.

Thank you, there seem to be a few good solutions that have been suggested. 

Currently testing scalability of my app so I borrowed a 32GB card. Interesting issues arrise when going beyond the normal case. Learned a bunch.