According to http://pulse.ncpolicywatch.org/2017/08/22/analysis-large-eff..., NC's efficiency gap is around -11, while anything in excess of +/- 7 is considered a very large gap, so by the efficiency gap metric NC's map is definitely extreme.

The recent coverage of considerations of the efficiency gap by the Supreme Court would be available here. The illustrative graphs provide a bit quicker of an introduction to the measure.

https://www.washingtonpost.com/graphics/2017/politics/courts...