Post like this drive me completely insane... I'm glad you are staying with Windows Phone, but your rationale is just plain silly that it's HTC or Verizon's fault that your phone was overheating. Let's take a look at the first 2 things to try - that you made no mention of... but first... Is this only when gaming, because when you heat a quad-core processor up in an aluminum body, it will get really stinking warm. That's not a problem, but a reality of high powered smartphones. The little dual-core in the 928 stays quite a bit cooler, but under intense gaming it will still warm up quite a bit as well. Now, if it was a constant thing, you should have...
1) Full reset - only install needed Apps. Then see if overheating continues - if it does, uninstall all Apps and see if overheating continues. If it does, you have a defective device. Head to VZW store and swap it out.
2) Full reset - install all your See if overheating continues - if it does, check your battery save for what is using the battery. You'll probably see something like MSN Weather eating up 45% of the battery and causing the problem. Also, check the number of background tasks running on a regular basis.
If those happened and you swapped the device and still had issues, I'd check the charger you are using to see if it is the original OEM HTC charger or if you damaged the battery using a $2 charger from Amazon or Ebay. Then I would make sure that you are in a good coverage area - the radios may not be the same between the two devices and it could be swapping CDMA to LTE constantly. You can switch off one or the other to test that theory in the SIM settings.
All in all, there's about 200 different reasons any phone can overheat, but more often than not it is an App constantly running. How as the battery life when it ran hot? Was it really short? If so, you had something running in the background that was using a ton of processor.
Again, sorry to lose you from the M8, but happy you're staying on with WP!