I know no-one reads this, but I've finally figured out the problem. The 4 (thats right, only four) screws that are keeping my pound-heavy cooler on my pcb are not tight enough. I can sqeeze the card during furmark and watch the shader temps go down instantly. I had the card mounted in a normal up-down Atx case, and while its on its side, and the cooler is not hanging down, I also saw better temps.
I dont have proper tools to tighten them, and have striped the screws while trying to do so. So now they are easily unscrewed, and hard to screw tight. I need new screws.
EDIT: I managed to tighten the screws just a tad and watched the shader temps go down from 140 to 100 in furmark. Looking forward to finding good tools and non-striped screws. (doh!)