I can clearly see more than two heatpipes in the images. So while the card may employ two 10mm pipes, it also has two 8mm or 6mm pipes in addition to them.
Consider the fact that Sapphire's Tri-X version has one 10mm, two 8mm, and two 6mm pipes and it's pretty obvious that only two 10mm pipes couldn't possibly draw enough heat away to effectively cool this GPU and its VRMs.
What we can't see from these images is if ASUS chose to implement any backside cooling for the GPU or VRMs. Sapphire chose to leave those areas exposed on its Fury Tri-X despite implementing a backplate, and IR images showed the VRMs reaching 90- to 100-degrees Centigrade. That's not just hot, it's very, very hot - fry an egg and boil water hot. And those components just sit there, exposed, leaking heat up into the CPU cooler?