OK, I’ve figured out a fix, and it’s definitely not what you’d expect.
After trying DDU and, since it yielded no results, entirely formatting my machine and re-installing Windows, the issue persisted. So, I’ve used Open Hardware Monitor to keep track of my PC’s parameters - temperatures, voltages, power, etc.
I was able to recreate the issue (playing WoW, alt + tabbing into Firefox and having the system crash) and noticed a very curious thing: the penultimate recorded TDP for my GPU was that of 180 W (all the surrounding values - including one last value - were a lot lower than that).
So I’ve installed MSI Afterburner (a software I’m familiar with since I used to OC this very rig before it started going unstable) and topped out the power limit to 112% (it’s a pretty safe power limit, in case you are not familiar with OC’ing) and ran the same scenario: playing WoW with multiple alt tabs.
After about 20 minutes, logging the parameters every 1 second, I was able to get one single recording of 200 W (among 1600 recordings). Here’s the plotted values (X-axis is the # of the recording; Y-axis is the TDP in W).
imgur-com/a/FeG1kxl
So, in short, there’s some shenanigans happening with my GPU that causes alt + tabbing from a game to be extremely demanding sometimes, and the system was shutting down because it was drawing more power than the default options allow it to. Raising the safe limit allows me to bypass this issue.
I understand the risks (mainly temperature-related - it’s not gone over 70 celsius, though), so, in case someone is experiencing a similar issue, please do be careful about the tweaks you make.