I don't get your problem here. Is it:
1: That different fires are treated differently?
2: That you have no problem running tenth level PCs through first level adventures? Because that's what a non-scaling world means.
The 4e rules say "All else being equal, you scale the challenge to the PCs level". This is a good starting point.
It might make it clearer for OSR players to put the damage expressions by approximate level of the dungeon as the rule of thumb rather than by level of the PCs. But this is again level scaling, and you don't expect tenth level PCs to mess around in the first level of the dungeon. (I once or twice have had a first level bandit rading party try ambushing high heroic PCs but only for comedy relaxation).
We are discussing
1: Level scaling and how this impacts play.
2: Worldbuilding in a world with hit points
3: Damage inflicted by fire.
Hit points are 100% relevant for all those things and are the clearest indication of how level scaling is built into the assumptions of D&D.
Except it does. For all the reasons I've gone into. The changing of the challenges you should be facing and the stark power differential across levels is baked into the assumptions of D&D and is shown at its clearest through the hit point mechanic.
Level scaling has been one of the fundamental assumptions of D&D right from Gygax and Arneson. And hit points demonstrate this. That you don't like this demonstration doesn't make it irrelevant.
A lot of good points here; especially the last part...
That is part of why I have said in other discussions that maybe I did not realize that some of the problems I had/have with D&D were also in 3rd Edition simply because I did not know any better. At the time -with few brief exceptions- my experience with rpgs was D&D. Once 4th came around, I was at point where I was made more aware that things could be done differently. Some of the changes I liked; some I didn't. Either way, the important thing was that I felt I had more insight into my tastes and what I wanted out of a game because I was given a greater awareness that I had choice and that different options were available.
Oddly, I credit 4th Edition with helping me to discover games that have more of a 'sim' element. While (in the beginning) I generally found 4th Edition to be somewhat at odds with what I wanted out of my experience, there were a few areas in which it seemed to tone down D&D a little bit. In particular, there was less of a power curve between levels; that was nice because my game didn't change all the time. I also enjoyed combats which had more moving pieces.
HP did seem bloated at that time. It always had, but it seemed somehow more. Perhaps it was the weakness of the opposition (monsters.) Still, D&D was what I knew, and I accepted the abstract nature of it. I accepted it until I tried games in which HP was not treated the way D&D treats it. I learned that I preferred a different way of doing it. Likewise, I also learned that I preferred being able to roll a parry, a dodge, or a block far more than having a static defense where I just stand there and get hit.
I think what I am trying to get at is that I often feel there are things in D&D which really do not make sense in any context outside of D&D. This is not meant as a bash against 4E, but, in other threads where I've mentioned some of why I felt 'disassociated' from the game, I think that is part of what I was trying to say. There are a lot of times when my mind really had no connection to what was going on. I had to learn a second version of reality -4E's reality.
As both a player and a GM, I was making decisions based upon that second set of reality. I often felt as though I was making decisions which the game said were right rather than decisions which felt right to me. As a DM, I felt that made it harder to design encounters because I was designing from a viewpoint which was often at odds with my own. As a player, there were a lot of times when I felt as though the right answer according to the game trumped what I felt would be fun.
I don't ask for a perfect simulation. I can and often do accept abstractions in the name of playability. However, as said elsewhere, I like to be in the same general ballpark. I do not view all disassociation as bad. However, if I feel that I often cannot connect with the game, I do view that as bad... at least in so much that I play rpgs to satisfy desires which are not the same desires behind why I would play something like parcheese.
Another place I find issue is when a game is not (imo) consistent with itself, and that is somewhere that I find the "4E Reality" breaks down. In my opinion, a world built upon how 4E works would look nothing like how many of the 4E settings look. Some of the things don't make sense even when I try looking at them from the viewpoint that 4E asks me to look at them from. On that note, I'll repeat something else I said elsewhere by saying that the most successful games of 4E I ran were ones in which I completely ditched to default setting assumptions. Instead, I went with games which embraced the somewhat gonzo nature of certain things. That went exceptionally well, and I was very happy with the results.
Unfortunately; at the end of the day, I feel as though I cannot use the system to tell a lot of the stories I want to tell. That is part of why I find the discussions about 'the narrative' the be somewhat alien to me. I find the system getting in the way of many of the narratives I want to have. I at times find that I have a hard time telling certain fantasy stories because D&D has evolved into its own sort of genre; moving a story from a genre outside of that into it causes the feel to change. The opposite is also something I feel is true and a big part of why I find myself using other systems to play some of the D&D settings.
None of this is intended as a slight against 4E. I do enjoy the game now that I have a better understanding of what to expect from it, and I am aware I have other options for when I want other things. I'm simply trying to give a little insight into why I feel the way I do about certain styles of mechanics.