You might be right.. I'll try out some more games + benchmarks.
I just thought it wouldn't be normal for a GPU to behave that way... as in using only 50-75% of it and the weird graphical issues on Sniper Elite v2
My GPU's are very rarely (if ever) running at 100% on ANY games (until I try to push them at 4K) so I wouldn't be too concerned about that.
As others have mentioned earlier, ARMA III is a CPU bound game which means it is CPU intensive and less GPU intensive, so its expected 'not' to push your GPU as hard as you might think. The graphical issues in Sniper could be an issue, but equally they could just be because the game is new and needs a patch? No idea really, which is why I think a wee bit of further testing would be beneficial if you can do it.
As I said, it might turn out that you indeed should get a new GPU (via RMA from PCS) but I'd try to be as sure as possible of that before trying to send it in