@bergauk and Grayfox Yes, yes, that's the first thing I did. Mates, I stripped the entire system apart, redid the thermal paste, clean out every nook and cranny possible. It's not dust, and thermal conductivity is fine now, it's just that the fan is restricted from being able to pull through enough air to cool the heatsink duct. It's fine up untill about 60% load, hell, it can even handle 100% CPU load, but as soon as both the GPU and CPU start working, things get very toasty very quickly.
EDIT: The other thing I suspect at full speed and full load, is that the fan isn't exhausting enough, and left over hot air is being pushed back into the gap between the bottom of the shell and the fan, and being sucked through again. Vicious cycle.