L401X overheating due to design failure

I am a royal user of dell. All my desktops and laptops are from dell. I even recommend dell to my friends. However this time I am so disappointed.

I purchased a xps l401x two years ago, because it was said to have optimus technique. In these two years, it frustrated me all the time. Whenever I loaded the nvidia 420m, for games or gpu computing, it would go overheating rapidly, no more than 5 mins. The temperature went above 75℃ or more and the gpu would be forced idle. I thought it was designed so and never really used it for these two years, until today. I found in dell community that replace the OEM thermal grease with some premium one would help. I desided to have a try. When I open the Processor Fan and Heat-Sink Assembly, I was totally shocked. There was NO thermal grease on the nvidia gpu chip. No wonder gpu went overheating all the time. Then I replaced the thermal grease on the intel cpu and added it on the gpu as well. When I turned it back on, the gpu temperature never went above 60℃ with 99% gpu load for a long time.

It must be a design failure if no thermal grease on the gpu. Otherwise, dell sold me a defective product. It feels like you bought a turbo car but drave for years without turbo because the turbo got overheating. Dell must do some thing like investigating this model or having them recalled. An offical public report for this problem is appropriate.