Alright, here's a quick update.
I've got no crashes ever since I disabled DOCP and put the GPU into "max performance" power mode. My PC has been running without any issues since Saturday so I decided to do some more testing today -- I kept DOCP disabled but changed the power mode back to "normal". Lo and behold, it crashed after about 12 hours or so. Now I'm testing the other way around - DOCP enabled + max performance power mode.
Is there any reason why the GPU would require the max performance setting to run stable? Is it a good enough reason to try to RMA?