It depends on how you play hp, saving throws etc.Why do you call them "metagame rules"?
If Mike Tyson thinks that he can easily defeat a dozen of 4 years old kids in a boxe fight, is he applying "metagame rules", or does he simply know what he can achieve?
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a frigging colossal dragon could hold a high level monk, with no armor whatsover, in his/her mouth, and breath acid/fire/youchoosewhat right on his face, with no saving throw allowed, and most high level PC would survive this attack.
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this high level PC should also have suffered several crossbow bolts / bow arrows hit in his career, even direct hits while he was helpless, and would know what damage he could reasonably aspect from them, and he could compare them to the cited dragon.
Now, I really can't see why his expericence with the dragon and the bolts/arrows should be seen as metagame rules.
If you play them as non-metagame (hit points = "meat") then the fiction will play out the way you describe. High level PCs are near-invulnerable (like Superman, The Mighty Thor, etc).
But - as per Gygax's description in his DMG - I treat hp in these situations as luck/divine favour. They're an alternative mechanic to fate points, but like fate points are (as I see them) a metagame thing: at the mechanical level, the PC survives due to having many hit points; in the fiction, the PC survives due to amazing luck or divine intervention. But the PC doesn't know (though might hope) that such intervention will be forthcoming.
([MENTION=63508]Minigiant[/MENTION]'s example of angels intervening to break a PC's fall is an extreme example of narrating such divine intervention. Think also the shooting/conversion scene in Pulp Fiction.)
This, in my view, is the answer to those who are worried that high level PCs will go cliff-diving for sport: in the fiction, they have no reason to take the risk that the gods will protect them once again. (And at the metagame level, I assume that those who are playing a game of heroic fantasy aren't interested in playing inane cliff-divers.)
If you want to play hit points as meat, obviously I'm in no position to stop you! I think that this is at odds with Gygax's approach, and it seems to be most popular among some 3E players. I don't think it works well for 4e, because it's hard to explain how compassion and encouragement from your friend can restore your meat (ie martial healing doesn't gel well with hp as meat). And I personally don't like the flavour it lends to the fiction. That's why I prefer fiction as metagame (and saving throws also, as per the 1st ed AD&D DMG - in 3E I recognise that saving throws are no longer metagame, but that's part of why I don't particularly care for 3E).