I have a 1080ti 11G-P4-6696-KR I purchased a week ago, and unfortunately because of stock I couldn't get the water cooler.  I bought the EVGA 400-HY-5698-B1 GTX 1080 Ti FTW3 HYBRID which arrived today, installed it, and immediately noticed a 50% reduction in speed.  The install was quite simple (background in PCB assembly).
 
After moving it from slot to slot, and the finally running it as the only card in the system I figured out I might as well move it back to the stock configuration.  After putting the original heatsink back on (and new thermal paste), I booted it up on noticed the exact same issue.
 
Here are a couple things that I wanted to document here that I noticed.
 
1) The thermal pads on the AIO were bleeding, that is everything around them was semi-stained from what appeared to be resin.  This held true almost all of the pads.
2) The GPU pump and surrounding copper was cool to the touch
3) The on board fan was not spinning
4) The instructions show that you should put the GPU pump on the 2nd to the last connector, and the fan on the last connector.  When I put back the original equipment, neither the 2nd or 3rd fan spun, just the first, which is leading me to believe that maybe the GPU pump itself was not pumping causing excessive current draw leading to the thermal pad bleed.
 
 
The card seems to operate, but in a limped handicap mode.
 
EVGA guys, please take a look at the observations I have posted.  I wish I would have seen the forum posts prior to purchasing, but the product was from EVGA and had good reviews 4.5 on 143 reviews and is Amazon's choice.
 
Here is something that might be super interesting
 
Pre AIO upgrade:
+-----+-------------+--------------+
| GPU | Power usage |  Efficiency  |
+-----+-------------+--------------+
|  0  |      275W     | 2.67 Sol/W  |
|  1  |    247W     |  2.87 Sol/W  |
+-----+-------------+--------------+
 
Post AIO upgrade (as well as reverting):
+-----+-------------+--------------+
| GPU | Power usage |  Efficiency  |
+-----+-------------+--------------+
|  0  |      0W     |  0.00 Sol/W  |
|  1  |    250W     |  2.89 Sol/W  |
+-----+-------------+--------------+
 
I'm thinking there is a sensor that's being killed by these pumps.  Maybe some uncoupled feedback from the pump coils or something, or maybe they are just being fried from no-op. I have uninstalled and re-installed the drives a few times now as well.
 
If anyone knows how to recover this, I'll save me an RMA, otherwise I will be following this up with an RMA, which I'm sure will be rejected, but we start there.