Still a software issue.!
I do not write things just for fun. Software and Hardware are connected to each other, if there is a bug or issue in the software (like in Yosemite with the freezing of the desktop), this will be reflected in hardware not working properly.
First, yes, I admit, these issues didn't come up before Yosemite so that leads us to the issue being only in software. BUT...if it were only a software issue, everyone using Yosemite with our MBPs would have this issue and it would be a much bigger deal.
You do actually mention that your problem began after upgrading to Yosemite, so the new software had some issues with the compatibility of the hardware. So not hardware defect from factory, but software bug. And NO, there would not be more people discussing it here, thats because the issue is just for Macbook pros with dual graphic cards, (Intel HD graphics and Nvidia Geforce), and not all macbook pros come with these specifications (just the high-end ones.)
I dont understand how people can think its a hardware defect from factory, its so weird. I have mentioned it before. If there was a hardware defect from factory, you as an consumer would have noticed the issue the first week of using the brand new 3K MacBook Pro Retina Mid 2012, not 3 years later after you upgraded to a new buggy OS X software.
On scenario:
1. Lets say in the year 2012 - 2013, apple made 2 batches of the macbook pro with dual graphic cards.
2. Nvidia made also to batches of the Nvidia GeForce GT 650M.
a. The first batch of Nvidia GeForece GT 650M v.1, no bugs or nothing.
b. The second batch of Nvidia GeForece GT 650M v.2, no bugs or nothing, just some new coding or components (needs some modifications i OS X to
integrate just right)
2. The fist batch of macbook pros retina was equiped with v,1 of Nvidia cards
3. The second batch of macbook pros retina was equiped with v.2 of Nvidia cards, and some new patch of OS X software was released to integrate the new components.)
4. In 2013 newer macbooks was released with newer Nvidia cards and Intel Integrated cards, the GT 650M v.1 and v.2 is history.
5. Modification in software must be done to integrate the new cards and still support older cards like GT 650M v.1 / v.2.
6. In 2014 apple are working on a new platform Yosemite, a new recoded operating system. They will support all macs down to the 2011-2012 versions, so coding to integrate all versions of graphic cards and external components must be done. The developer have made a mistake early on, in the core/kernel function that supports the GeForce GT 650M v.1 - Intel HD Graphics switching.
7. They Release Yosemite, the customers with MacBook pros retina 2012 "first batch" with "first batch of Nvidia GT 650M v.1" notices that they get freezes, but the people with second batch with Nvidia GT 650M v.2 does not notice it.
The case above is a real life scenario, and it shows how a glitch in coding (software) have an affect on hardware. There is a silver line between software and hardware. So if a compony or developer have made an error in integration process, one or more products with the spesific types of hardware will fail (NOT problems with hardware from factory).
If they run a diagnostic and no problems is shown, you'll get you mac back, no replacements parts. My mac passed all tests, got it back nothing replaces.
If they send it to repair and change the logic board with the same logic board produced when you MAC was bought (Batch 1 Macbook, Batch 1 of Nvidia Geforce GT 650M v.1), the problem will occur.
BUT, if you get a newer logic board and graphic card,from ex: "batch 2 macbook pro retina 2013, batch 2 of geforce gt 650M v.2" this may solve the problem. If this is the case, apple development, have made a mistake down in the Core/kernel that is so expensive to correct (needs many man hours and, total rewrite of code) so the easiest way is to replace some parts. (Still a software problem, no hardware defect).
I am still waiting for an update of Yosemite.