This phone has been notorious for the battery draining and also becoming really hot.
The purpose of re-opening this discussion is to state the solution I found which many users have shared with the Verizon HTC M8 for Windows.
I have received a replacement HTC M8 for Windows and have not had any issues with my phone (no disabling GPS, no disabling Blue-tooth, no disabling the Verizon, no disabling Cortana, no disabling background tasks, no disabling wireless, and etc)
The issue is that Verizon supplies an incompatible power cord. With my old phone which was having all the issues, it would also sometimes have troubles charging. I went through my stash of phone charging cables until I found one that limited the charging issues. I know that there are two types of phone charging cables - 1) has purely charging capabilities and 2) has a data line to connect your phone to your computer, etc. I think it might be the purely charging cables which cause the issue because, as has been noted by other users, you cannot use the Verizon issued car charging cable. I am not sure which of these two cables I am currently using but my current cable works perfectly.
The Verizon issued cable broke my old phone. I ordered a replacement HTC M8 for Windows and have strictly used the charging cable I know that does not cause problems. I have had absolutely NO issues with my phone since I have been using the working charging cable. However, I am very cautious now about what charging cable I use with my phone.
The problem seems to be a hardware issue. Personally I don't think HTC phones have that great of quality, but Verizon does not supply a large number of Windows Phones. My last phone was a Lumia and that phone worked great. I dropped it all the time and had absolutely no issues with it. It was a quality phone. I really wish Verizon would be more cooperative with Microsoft and supply some higher end Windows Phones, preferably Lumia or Microsoft branded phones that I know are built well.
First of all, it is NOT a Verizon issued cable. The cable is provided by the manufacturer. Second, it's Microsoft who needs to make cdma enabled devices. CDMA carriers cannot force a company to make handsets that are compatible and even if they could the amount of people wanting them are so small it would not make a great financial decision.