Huh that voltage seems a bit high for my taste, what are the temps under load?
Don't have a DC2 just a reference design 290x but mine gets unstable on the core at about 1200 no matter what voltage I try (card is watercooled).
So you might have had bad luck with that particular card. How is the second one clocking?
You could also try changing the RAM clocks, some people suggested there is a sweet spot in RAM / GPU clock ratio that leads to higher overclocks.
