The falling damage is just rediculous. The armour has nothing to do with it, since you receive as much naked. Geralt loses half his HP jumping from a height that would left a normal person pretty much unharmed, not to mention a witcher. And the thing is that withstanding fall damage even while wearing armour is something that is specifically adressed in the books. It says something in regards that Geralt jumped of a ledge that would kill a normal person, without a scratch, and then he started butchering some Scoiatel.