Flickering/Rolling Black Lines on HD8970M
Update: Running the game in Compatibility mode for Windows 7 (Laptop is 8.1) appears to have resolved the flickering at the expense of a 30% framerate drop :P
Your exact issue was resolved in this topic about a month ago but with an R9 M290X (rebadged 8970M)
https://forum-en.gw2archive.eu/forum/support/tech/AMD-R9-m290X/first#post3880851
no compatibility needed