In every other game I've seen with fall damage, fall damage can be lethal if you land hard enough. I don't see any reason why AVWW should be different.
Something I am a bit more on the fence about is how fall damage interacts with health buffs.
In most games I've seen with fall damage, health buffs increase the distance you can fall (though if you are using a polynomial equation to determine fall damage, a large amount a extra health may only net you a little extra fall distance)
I agree with all of this. I think that losing three quarters of your health rather than all of it, on account of having upgraded it a few times, is as much preparing for the fall as equipping an enchant which will help you float down.
Furthermore, since there's no way to accurately judge quite how much any given distance is going to hurt, it's inherently more risky just to throw yourself off and hope your health soaks it up.
Spending all your upgrades on health
should make you feel more resilient to the environment, although it needn't be as tame as before. If you choose to forgo a proper falling enchant in order to max out other stats because you have spent so much on health, that strikes me as a perfectly balanced choice, given the inherent drawbacks of throwing yourself off cliffs with no way to directly heal yourself at the bottom.
In short, I'm all for the idea that on standard health (or on any health, given a long enough fall) you might kill yourself - but it should be based on neither a % of base nor a % of total health. A fixed amount of damage seems more sensible. Same goes for water/lava/etc.
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