The most important point to make is, Furmark is unreliable, doesn't always fully load the gpu and is incredibly inconsistant, even if it was, Furmark has zero bearing on gaming or gpgpu workload performance or power usage, its a completely and utterly pointless program that causes dangerously high VRM temps on many cards for no reason other than some douchebag wrote a program to see how high power draw can get under worst case scenario.
Kombuster literally has no valid use, and as shown by a few idiotic reviews who put on 3rd party cooling without suffient VRM cooling, then loaded up furmark and killed their cards, thats about the only useful outcome I've ever seem Furmark/combuster accomplish.
As shown above, results are ridiculously inconsistant, as shown by MANY reviews furmark loading is inconsistant, most of the time it will indeed load up your gpu way higher than anything else will, often, it won't as shown by several reviews that showed a second 480gtx/470gtx/5870/etc, etc only adding 50-100W, when under gaming the power usage will go up 250-280W for a 2nd 480gtx.
Sometimes furmark does give somewhat accurate results on sli/xfire, mostly not, sometimes its inconsistant in single card, IE, its utterly useless.
Also pointless for testing for overclock stability as game stability is almost always at a higher level than Furmark will say is stable.
AS a benchmark its completely unreliable. As an overclocking stability test, its inaccurate to real world usage, as a power monitor, its inaccurate, and those are the three things it was built to do, therefore, worthless.