I've posted over at /r/nvidia but might share my experiences as well here.
 
Edit #5: Bios update didn't help. Now running a pretty steep fan curve starting at 20° with ~600rpm, going into 2600rpm at 50° and up to 2800pm at 50+°. The board (likely vrm) seems to be cool enough now to run a good while. Though the card is likely going into RMA because i have to assume that the lifetime of the components has already been significantly reduced. But i doubt they will do more then install some heatpads.
 
**Edit #4:**
With manual cooling and downclocked vram, problem didn't occur again. Could be a concidence. EVGA suggested applying this bios update: Testing.
 
**Edit #3:**
Happened after just ~30 Minutes with only vram downcklocked and letting the fan run on auto control. Backplate was very hot. I'm now doing both methods and see how long i can manage it to keep running this time. Tomorrow i'll get in touch with evga support.
 
**Edit #2:**
Happened again after ~4 hours regardless of additional cooling. Upon checking, backplate was warm but not hot. Easily touchable. I'm now downclocking the vram.
 
**Edit:**
What i'm doing right now is, i set the fan to 2400rpm at all times (~70%) to archive more cooling of the whole board. I've run 1 hour of FireStrike Ultimate and 1 hour of Time Spy. Now i'm using the machine like regullary. Till now it's stable. This afternoon i will try going with auto fan speeds again but clocking the vram down to ~3400MHz. If i'm fine it's very likely that my card suffers from the same vram problem as the FTW ACX series does.

My sob story:
Approximately two weeks ago i started to recieve supposedly random 'black screens' during gaming, forcing a reboot. Other applications like media servers or teamspeak continued to run even after the black screen occured. A look into the windows event log showed that the only thing that crashed where applications depending on an rendering interface. Those who crashed, crashed because of draw calls being not executed which matched my observation from before.
 
So, my first assumption was that the reason was either the PSU or Heat. I checked heat first - even under full load it rarely went over 72 celsius, which is absolutly fine. I didn't have a spare PSU so i removed the GTX 1070 and plugged in two Radeaon RX480 4G and did some crossfire benchmarking. No problems (They should draw more then double from the pcie connectors).
 
I did the obligatory Prime95 test to check cpu and ram as well. No problems.
 
I also did a clean windows 10 installation (including updates) with the 373.06 drivers. Error still occurs.
 
So i went to the googlemobil and found quite some occurences of gtx1070s having trouble with black screens. However the fixes where quite random and in some cases didn't make sense to me (like disabling hibernation). Most of them went into RMA.

The only thing which was noticeable, was the fact that they all popped up after the windows anniversary update in october, which i also have installed since about three or four weeks. However, this might be a concidence since the cards aren't out much longer. However, before i go into a multi-week long RMA i wanted to ask if anyone has some suggestions. Any help much appriciated.
 
Components involved:
* 630W Power Supply
* Asustek P9X79 DELUXE
* i7-4930k
* EVGA GTX 1070 SC ACX 3.0
* Connected to a 1440p monitor via display port. No other display devices connected.

By now, i'm guessing you're right. 
 
I've added a custom fan speed curve with the assumption that the vrm will always be ~40° hotter then the gpu. With 2600prm at 55° gpu temp, the system seems pretty stable. Currently running furmark.
 
Question for me is: Going into RMA now and have to buy a spare card for the meanwhile or wait until it will inveitably break, go to the retailer and get a new one.