... Here's the new system: when you're in Kur, an additional bar will be shown along the top of the screen labeled "Body Heat". While you've got some body heat left in the meter, you're fine. No ill effects from the cold at all. Your body heat drops over time, and when it reaches zero, you get frostbite. And if you stay at zero for too long, you get hypothermia, which is almost certainly fatal unless you get indoors fast.
Your Indirect Cold Mitigation will still play a key role -- it'll affect how quickly you lose body heat. Cold-weather gear like fur parkas will boost your indirect cold mitigation, and they may also boost your maximum body-heat, so you can travel for longer. And some items and abilities will have a chance to boost your body heat, too. Breathing fire seems like it should have a chance of giving you back a point or two... and Ice Magic would likely have some tools to survive in the cold...
I hope that this system will be more intuitive than the old system, because "don't let your bar get empty or you die" is easier to understand than "you take lots of cold damage all the time, but when you're out of combat your food recovers the energy, so it's only when you're in combat that it's dangerous, and if you go below 50% health during combat you might get hypothermia". There's still a random element: the rate of heat loss is not constant, it happens randomly based on your cold mitigation. In colder areas it drops faster than others. (For instance, being submerged in Kur's ocean is much colder than being on land.) But I think the extra GUI bar makes it all a lot more understandable.
I'm still refining it and trying new things, but I wanted to give you an idea of where it's headed. To reiterate, though, my goal is NOT for Kur to be a huge pain in the ass all the time. The goal is for Kur to be a predictably dangerous environment that you have to take precautions for. At low level it's very dangerous, but at high level you only need moderate precautions.