Best 24-70 f/2.8mm for handholding on D800?

In my short experience with the Tamron there has been troubling levels of sample variation. Also Roger C. at Lens Rentals reports a 10% failure rate of the second lens element falling out of position, which he thinks might be because it's glued into position rather than shimmed (Article). Fortunately the Tamron comes with a 6-year warranty which includes a 3-day turnaround, which Roger reports as being accurate.