So, TSSAA (8x) plus Ultra and 16x AF, I'm seeing no lower than 90FPS at 1080p with the average being over 100 but under 115. The GPU is constantly pegged out and my 390 is running a lot hotter than it normally does at full load, normally I'll see ~70*C under load but, I'm seeing about 80*C with this. I would say, that Vulkan is doing a pretty good job at tapping those unused resources. My only complaint is that TSSAA, even at 8x is kind of meh. Either way, I'm impressed with what I'm seeing. I think I'm going to see how eyefinity runs. I'll report back.
Edit: I'm noticing some flickering at far distances. It could be the TSSAA, I guess.
Edit 2: Flickering went away when I turned off AA. Funny thing is that frame-rate didn't change much after I disabled it.
Edit 3: It appears that TSSAA (8x) seems to be the only mode that causes flickering.
Edit 4: Same scene does about 39-60FPS on 5760x1080 which is far better than I was seeing before but, it isn't what I would consider acceptable. This is with the same settings as at 1080p, Ultra + 16x AF + 8x TSSAA. This is also with no overclock on my GPU with the stock 1040/1500(6000).