RottR is using a caching system as far as I know, like the Frostbite engine used in the BF games. It'll use more if you have it but it's not required. GTAV is just a hog.
haha. Witcher 3 is arguably the best looking game on the market right now, and I see 3GB vram usage on my 980TI at 3440x1440. 3GB !!! It's more due to the inefficiency of the other games imo, which might change in the future -- who knows.
Agreed on NV's compression capabilities. On my 3440x1440 monitor, I don't see a single game going over 4.5GB of vRAM usage. I'll try Rise of the Tomb Raider later on my 980TI, but I know on the TITAN X SLI system, it wasn't even hitting 6GB out of the 12GB available on the same 3440x1440 monitor.
I am very curious how Deus Ex and BF1 turn out with DX12 usage, but I also suspect NV's performance will have improved by then as well.
As for the 1070 + the AMD CPU ... nooooooooooooo !!! The 6700K @ 4.4Ghz will probably end up faster than Zen anyway.. lol.
Big Pascal is where I feel DX12 performance really improves.