What you see as flickering/shimmering is normal due to the game not having real AA. It's been like that since the beginning (of ARR)

The only form of forced AA that works with the engine (as far as my tests go) is SGSSAA and even then for a flicker free experience you'd need to down sample from 4k to 1080p. For reference, single GTX 980 can barely pull this off.