Brushing and spot healing are known to cause this type of problem. The best workaround is to use the Photoshop editor (not ACR in Photoshop) to do the brushing. You will also see a speed improvement for brushing and spot healing by turning off the GPU acceleration in Lightroom. One last thing you can try is to not do any lens corrections until you have finished the brushing.
You didn't state the dimensions (in pixels) of your monitor, but the benefit from the GPU acceleration generally only becomes helpful with 4K and 5K monitors.
My screen is at 3840x2160.... it is a touch screen as well.... there is integrated graphics Intel HD 5000 along with the dedicated graphics of 4GB AMD Radeon R7 M270...
I have had no such problem with lightroom as mentioned above when it comes to my lower end system.....
I also forgot to mention that photoshop is so slow that when for example i open an image and try to edit it using the curves, it renders block by block.... it doesnt move according to my slider/ graph, but it renders like 5 seconds later patch by patch.
I am really getting frustrated with the way this is running. I just hope that its nothing to do with the software, that is Adobe CC.
Need help on this, coz im really driving Dell mad, as such a high end system cannot outmatch my lower end system ( specifications mentioned above in first post)
As I said, you want to turn off GPU acceleration in Lightroom to help increase the speed of your brushing.
I have the same problem too with brushes, except turning off GPU acceleration will then affect the speed of the regular adjustments tool such Exposure, Shadows, Highlights etc. It's simply unreasonable to have to turn on and off for each image that we work on.
Does anyone know if Adobe is indeed working on a solution for this?