I don't know your experience both personally or with clients, but I would have to say on the whole you are mistaken. If the standard were that these dual graphic boards were failing as frequently as you suggest, there would be some form of recall, I would suspect.
That said, I have owned two macbook pros and never had a graphics related issue.
I am confused, you cited black screens and kernel panics, but those issues are not solely due to IGP or GPUs. Do you have any sort of data to back up your claim, or is it just personal experience? I only ask because from my personal experience, I have yet to meet an individual who has had a GPU related hardware failure. Does that mean they don't exist? No. It means my sample exposure is the complete other side of the spectrum.
If you have any data on the dual graphics boards stating that their chance of failure is as high as you suggest, I would genuinely be interested in reading it.