I know you are going to question this suggestion. However, it's worth a try. Go to Lightroom preferences, performance tab, and uncheck the GPU option. See if it makes a difference in performance. I understand you have installed the latest/greatest in this computer, but GPU seems to be causing problems with some computers.
Now, there used to be NO latrency, however, it seems to have crept in. When starting Lightroom CC, the catalog files on the left (in the Windows Explorer style list) can take up to 8 seconds to populate now, showing little 'dots' while we wait for it.
I'm seeing the same behavior with LR CC 2015.4 on my Windows 7 system with more modest hardware. I don't know when this changed, but it shouldn't stop you from editing the files. You can access the files in the folder immediately even though the file count number hasn't appeared yet.....at least on my system.
Also, when using a brush with a tablet, when you move the stylus, there may be a slight lag, about a half second, or second, which is VERY off putting, as you can imagine. Like I say this isn't ALWAYS the case, but 9 times out of 0, it is. I have been through the setting for PS and Lightroom with regard to it using the correct video card etc, but no joy.
You should be aware that currently the GPU is not used to accelerate the Adjustment Brush:
"Within Develop, most image editing controls have full GPU acceleration, including the basic and tone panel, panning and zooming, crop and straighten, lens corrections, gradients, and radial filter. Some controls, such as local brush adjustments and spot clone/heal, do not -- at least, not yet."
Full article by Eric Chan, Adobe Engineering: GPU notes for Lightroom CC (2015)
In fact unselecting 'Use Graphics Processor' as JimHess suggests reduces the Adjustment Brush latency on my system. Intuitively, this shouldn't have any effect, but it does on my system! See this reply: