I think you are right that the 390 is the best card you can get for that tier. And you are right on about memory being a concern for the gtx 970. Tomb raider is already pushing 4 gb at ultra textures.
You can try underclocking your memory and putting the overclock back on your chip. Maybe see if that stops the artifacting.
To me, the artifacts are a concern. Its one thing if you are crashing the driver. That suggests conflict between the drivers and the game or general instability of one or both. But when you get artifacts on a mild overclock, that starts to suggest hardware problems imo and would make me start thinking about RMA.
it hasnt artifact at anything from stock to an oc of 1100 from the stock 1040, just above that, artifacting slightly at 1010 and stock voltage. never atrifact at all at 1040 with bumped voltage, at least not in the witcher 3. all that happened was i was at a bandit camp, slain enemies started floating in air and then fps dropped. since then the game hasnt ran as smooth, but its inconsistent. at times its smooth as can be and at others not. and its doesnt drop during cut scenes or even hectic battles, which is why im thinking its possibly the game. perhaps simply being a nvidia gameworks title on a amd card? idk, ill wait awhile, play a few games and see if it still acts up.
it seems like every video i watch of the game has this microstutter going on, and ive noticed that its most prevalent while playing when i move the mouse. a lot of complaints about it on the net, and it appears to happen even at high fps. a number of people suggest its an issue with with the game engine/camera and not hardware performance. they also complain about it suddenly occurring out of nowhere after the game had run fine for hours.
