In the post-Kaby Lake era, I'd argue that it's pointless to say that AVX and AVX512 are "more stressful" than normal code.
The reason I say that is simply that AVX(512) aren't supposed to run at the same speed as normal code anyway. For the same reason, nobody runs their GPU at the same speed of the CPU. AVX and AVX512 fall somewhere in between.
To oversimplify a bit, a Skylake X chip has 5 different sets of silicon that run at different speeds:
Main core.
AVX units
AVX512 units
uncore (L3/mesh)
DRAM
Most people are familiar with 1, 4, and 5. But very few people are aware of 2 and 3.
Most of the people who get "burned" (pun intended) by AVX or AVX512 either don't know about the existence of 2 and 3 and therefore are likely to set them wrong. Or they are aware, but don't realize their importance and thus ignore them. And from what I've been reading online, it seems to be a good mix of both.
Back in the Haswell/Skylake (non-X) days, 3 didn't exist and 1 was tied to 2. So you were forced to drop to down to the lower denominator. This is what gave AVX its bad rep among the OC community in the first place. But this bad rep seems to have stuck even after Intel has fixed AVX by separating 1 and 2 into different classes (which it really should've done from the very beginning in Sandy Bridge)
The problem now is that because the chip is so complicated now, it's become increasingly difficult to stabilize it against all workloads. So it's easy to screw up. And each time someone crashes on AVX or AVX512, it just adds fuel to FUD that "AVX is bad".
So I'm interested to see what the rest of the OC community does with the new Prime95 with AVX512.