Originally Posted by 3vodroid
.. maybe i'm just too picky lol.. [I] just have high expectations for the phone and don't want to have any more issues
You are in good company
It is ok to have opinions and I think you should not give up until you find a resolution that suits you.
Can you carefully swap a battery door with a friend that has an Evo 3D as a testing measure? Be careful not to get them mixed up when trading back.
If not, some people that use exterior protecting cases have liked their power button more after installing a case.
Ebay has some battery doors listed. BEWARE Ebay is a crapshoot. These two sellers seem pretty legit though (I'm not responsible for anyone's decision to purchase).
NEW OEM SPRINT BLACK HTC EVO 3D STANDARD BATTERY DOOR BACK COVER FREE SHIPPING | eBay
NEW OEM BATTERY DOOR BACK COVER FOR SPRINT HTC EVO 3D | eBay
Check in with Sprint again and give them a shot.