ETTR is still subject to much misunderstanding as originally conceived.
When this is combined with the current shifting of the goalposts created by the newer Sony sensors (the point Slobadan was making) greater confusion is possible.
The OP, in introducing the topic of ETTR, gives an example of a shooting situation where trying to apply ETTR principles does not make sense.
There was never any chance, due to the combination of light and subject (moving goats), of shooting at base ISO.
Shooting at base ISO (as already stated) is absolutely fundamental to the point of ETTR - which is to reduce noise generation.
Technically, Slobadans point about guessing what the real highlight exposure cutoff for one's sensor is incorrect since this information can be easily sought. In practice I have learn't from trial and error how far I can push exposure in the ETTR context with the cameras I use with excellent results.
The postprocessing involved in "normalizing" the exposure, with a little bit of practice is simplicity itself. I do not use a preset in this process. I always use a 'season to taste' approach.
It seems that many individuals are trying to apply principles of ETTR to situations that make no sense.
So, if you are shooting at high ISO for any reason trying ETTR is a nil sum game.
It is possible to use ETTR in poor light scenarios if the camera is on a tripod and the subject of the image is static - shoot at base ISO and use the appropriate (long) shutter speed.
Shooting live action in poor light (the OP's example) ETTR cannot work, simple as that, since any sort of image quality will require fast shutter speeds and hence appropriately high ISO's.
Also don't try ETTR if one has to shoot RAW and JPEG simultaneously (seems a no-brainer but this does confuse some).
Could the principle of ETTR become redundant going forward? Yes, possibly.
I don't own a D800, or any other camera that contains a recent Sony Exmoor sensor, however it is clear that the image quality obtainable from these cameras at high ISO's, not to mention future developments, may make the concept of ETTR redundant.
I am not sure if anyone who owns a D800 and is intimately familiar with ETTR has yet contributed to this post.
Slobadan may be pointing us to a time where ETTR will be of interesting but historical interest.