It was the DC2 that was having issues with the heatpipes. I think this may be able to be fixed by using a copper shim? If you look at the cooler for the 7970 DC2 Top you can see they have another piece of copper across the heatpipes to make sure the heat is distributed. Why they didn't do this in the first place is a mystery though!
Warning: Spoiler! (Click to show)
Edit: Also noticed the 7970 has 6 heatpipes and the 290 only 5... Granted one of the pipes on the 290 is larger, but why would they do this?
Does this looks familiar:
That's the DCUII 780 Ti cooler, which came out before the DCUII 290x.
Or how about this:
That's the DCUII 780. There has been very little change from what I can see on this cooler and ASUS thought it will be great for all GPUs