Players cannot stay inside the Temple of Frost because it gets cold very fast ending in Frostbite. Also, at the South of Blizzard’s Overwatch it gets extremely cold very fast and must run back towards the South again before getting Frostbite.
I’m pretty sure that this is intentional. With warm armor, and some warming food and alcohol, you should be able to survive there just fine. It’s even easier if you take the vitality perk that makes you more resistant to temperature.
Is that why the vanir armor cold resistance was changed?
That’s a great question but only the Devs can answer that. Maybe it’s because it shows so much skin though.