to me it seems like it's not the GPU heated up that caused the 3RRoD.
The 3RRoD is just identifed as General hardware error which can be related to everything in the system....
What I'm going to discuss about is the broken GPU soldering...
As we know PC's GPU will also become very hot when fully loaded and sometimes up to 95C and they never seems cooked....or AFAIK they're not.....
For me it looks like somehow the material they used, be it circuit board, GPU casing or the soldering itself is not heat tolerant.... and I'm don't understrand why the material is not changed till now..... PS3 or Wii will also overheat but they never suffer from broken solder joint.......
So, basically reducing the thermal junction problem between GPU/CPU core casing and mainboard seems more promising to eliminate the broken soldering problem....
How? haha, conclusion back to square....use a better heat solution OR A/C blast which might risk condensation to suck as much heat as possible from the cores.....you cannot dissipate heat on mainboard as quick as the CPU/GPU core even with a very good heatsink
This is why M$ will never solve the problem unless they change the material used OR design a core with no excessive heat dissipation....something like Transmeta Crusoe processor or Intel Atom processor