Ok, so after doing some more tests, I think I've narrowed down the issue.
As some may be aware, GPUs like the Asus Strix and MSI's Gaming X come with different modes that you can set using the manufacturer's app, typically silent mode, "gaming" mode, and an overclocked mode.
It seems setting it to OC mode may be causing instability in my GPU, hence why it freezes. So either I really got bad luck in the silicon lottery with my 1080 Ti Gaming X, or the factory overclock is drawing way more power than expected.
I'm surprised if this is the case, as factory overclocks tend to be very modest compared to what's possible with manual overclocks.
I'll keep testing with the above assumption to make sure. But it seems the GPU is most stable at default settings.