I think Kombuster is DX11 only, I'm not sure, its just MSIs versions of Furmark they are like the exact same thing, just use Furmark instead.
I could be incorrect, but to save hassle just use Furmark.
I found this cached in an old Google Result that lead me to the conclusion..
well i think its not fair that you can only use kombuster for dx11
I don't know what they are talking about, but seems to go wtih my original conclusion.