Roughness values should always be in linear space - you will get inconsistent results with sRGB. In terms of reference, have a look at this: https://seblagarde.wordpress.com/2014/04/14/dontnod-physically-based-rendering-chart-for-unreal-engine-4/
Turns out this is a known issue: https://forums.unrealengine.com/unreal-engine/feedback-for-epic/106544-dynamic-shadows-artifacts?133869-Shading-problem-in-4-14=&viewfull=1
There most definitely is :) Realtime dynamic lighting and shadowing in only 7 colors, well technically 14 colors, 7 shades of blood and 7 shades of everything else lol.
Update on WA: Monolith 6 ArenaNet 14 Microsoft Game Studios (?) BlackPowder Games (?) NST (Nintendo Software Technology) (?) //Snowblind no longer exists. (Merged with other studio)