You might have a lemon, as Edmund suggests, but you are aware I presume that pushing exposure to its maximum at high ISOs is crucial for a relatively noise-free image.
What has become apparent to me recently, as a result of some of the more technical members of this forum analyzing one of my RAW images, is that ACR can sometimes do an excellent job in disguising overexposure.
What I'd be doing in your circumstances, is setting the camera to TV mode, choosing a shutter speed that you assess is right for scene movement (or camera shake), and then autobracket exposure (through changing aperture).
You will then have a greater choice of images. For example, one with greater DoF but higher noise; another with less noise, but shallower DoF.
I wouldn't bank on the 1Ds3 having significantly better high ISO performance than the 1Ds2.