I'm going to
I now feel better about those, but the crashes are infuriating!
You're right on this. I do need stress the card another way. Research has also found other AMD users with the same artefacts: http://forums.playbattlegrounds.com/topic/4689-black-boxesshadow-bugartifacts/You're having a tough time of it...
I hate to say this but again you need to try a 'full release' game that's been patched to the eyeballs - e.g. battlefield 1/4, Farcry 3/4, Blackops etc... Basically any big backed game that's gfx demanding and has had resources thrown at it to make sure it's compatible with mainstream cards.
If it still gets artifacts, with a full release title (fully patched), and BIOS set to defaults etc (nothing clocked) - then you would certainly have to begin to suspect your card.
I now feel better about those, but the crashes are infuriating!