Unfortunately, you are not alone.
PC Sounds like a Jet Engine - Technical Support - Diablo IV Forums (blizzard.com)
GPU Load Increase While Talking with Vendor - Technical Support - Diablo IV Forums (blizzard.com)
GPU going mad in inventory / vendor menu - Technical Support - Diablo IV Forums (blizzard.com)
Best thing we can do it be vocal and keep these threads at the top.