There appears to be a bug affecting all recent versions of Lightroom on high-DPI Windows devices. It affects both CC and standalone versions, up to and including the current version (2015.6.1).
The issue is that when using the white balance dropper tool in the Develop module, the target location Lightroom uses does not correspond exactly to where the point of the dropper is located. Specifically, it seems to reference a position about 5 or 6 millimetres above the point of the tool.
The issue also affects the manual defringe dropper in the Lens Corrections panel. Other local develop tools seem not to be affected (brush, spot healing, HSL/Color/B&W picker, etc.).
To be clear: the issue affects Lightroom when the device is used in standard desktop mode with a regular mouse as the pointing device. It is not an issue with the touch screen, the pen or Lightroom's touch mode.
The problem is described in detail with screenshots here (in the original post and in my reply):
It's also discussed briefly here: