Matrix R9 280x please help

[chuck_norris]

Hi All,

I'm having an issue with my Matrix R9 280x where i am getting lots of artifacts. It was happening very rarely but then when i bought
GTA V and FSX it started getting worse. I RMA'd the card in May this year to the retailer as this is what was advised by ASUS support.
They said they tested for 24 hours using heaven and other game benchmarks and there were no issues so i got charged stg£38 for the
privilege.
It kept happening especially on GTA V and FSX since then and now that i've bought Starcraft II - Legacy of the Void it's terrible after only 1 hour play!.
I ran heaven benchmark after exiting the game and it was artifacting bad, i shutdown the PC and restarted after a few minutes and back to normal,
there are no artifacts on Heaven benchmark or Furmark over 2 runs (approx 15 mins)
I'm afraid if i RMA the card again the same thing will happen and i will be charged another stg£38 for nothing. There is no doubt in my
mind that the card is defective but i want to ask here for someones opinion on what i should or can do?

My system specs are as follows:
Rampage IV Black, 4960X, Corsair H105, 16GB HyperX Beast 2400, Coolermaster V1000 PSU, Samsung 840 SSD's

Any help would be gratefully appreciated!

Many thanks,
John