This is one of the philosophical beefs I've developed against discrete GPU's, particularly in laptops. I've been using 13" unibodies with iGP's (Sandy, Ivy, Hassy vintages) and haven't had any of these problems. Bad stick of RAM, sure, but I blame samsung or whoever their supplier was. But most of the MBP deaths I've heard about from friends have been with AMD/nVidia GPU daughter cards on the 15's. My rMBP 13" also h…
Why the beef against discrete GPUs? Shouldn't the complaint be against cases not properly designed to house them? MacBooks also use, quite frustratingly so, damn near the slowest Nvidia mobile GPU you can buy! A newer model might actually run faster and cooler.
The reason this matters is because the process by which those solder balls are made does not check for the presence of voids in them. At least 10% of these balls (regardless of composition) x-ray as having voids.
GPUs go through the most radical thermal shifts of any surface mounted component. Lead has a sense of humor about that kind of temperature change; tin alloys do not and begin to crack after a sustained number of shifts. This happened on my 2011 MBP which was not used for gaming.
It's worth noting that the iMacs made the same year, where the discrete GPU was a replaceable daughtercard, had a voluntary recall for exactly the same reported video problems. The irony here is that the average cost of having a GPU reballed is about $150US, with a high rate of reliability compared to reflowing. Part of that reliability comes from reballers refusing to use anything but lead.
The EU is directly responsible for this problem but Apple is responsible to its users and with a cash reserve outstripping the US Treasury's, could have absorbed the cost of repairing these MBPs easily.