Philmo shares an article by Justin Alexander from 2007 that shows me I've been thinking about D&D all wrong for a very long time:
D&D: Calibrating Your Expectations
There’s a common fallacy when it comes to D&D, and it goes something like: Einstein was a 20th level physicist. So, in D&D, Einstein – that little old man – has something like a bajillion hit points and you’d need to stab him dozens of times if you wanted to kill him. That’s ridiculous!
The problem with this argument is that Einstein wasn’t a 20th level physicist. A 20th level physicist is one step removed from being the God of Physicists. Einstein was probably something more like a 4th or 5th level expert. [Emphasis mine]
This can be a little bit difficult for some people to accept, so let’s run the math. At 5th level an exceptional specialist like Einstein will have:
+8 skill ranks
+4 ability score bonus
+3 Skill Focus
In the case of our 5th level Einstein, that gives him a +15 bonus to Knowledge (physics) checks. He can casually answer physics-related questions (by taking 10) with a DC of 25. Such questions, according to the PHB description of the Knowledge skill, are among the hardest physics questions known to man. He’ll know the answers to the very hardest questions (DC 30) about 75% of the time.
And when he’s doing research he’ll be able to add the benefits of being able to reference scientific journals (+2 circumstance bonus), gain insight from fellow colleagues (+2 bonus from aid another), use top-of-the-line equipment (+2 circumstance bonus), and similar resources to gain understanding of a problem so intractable that no one has ever understood it before (DC 40+).
(This 5th level Einstein can also be modeled with as few as 5 hit points – 1 per hit die...)
Alexander goes on to run numbers on a variety of performance benchmarks that back up his thesis:
5th level is right at the dividing line between legendary real world performances and the impossible realms of the superhuman.
Almost everyone you have ever met is a 1st level character. The few exceptional people you’ve met are probably 2nd or 3rd level – they’re canny and experienced and can accomplish things that others find difficult or impossible.
If you know someone who’s 4th level, then you’re privileged to know one of the most talented people around: They’re a professional sports player. Or a brain surgeon. Or a rocket scientist.
If you know someone who’s 5th level, then you have the honor of knowing someone that will probably be written about in history books. Walter Payton. Michael Jordan. Albert Einstein. Isaac Newton. Miyamoto Musashi. William Shakespeare.
So when your D&D character hits 6th level, it means they’re literally superhuman: They are capable of achieving things that no human being has ever been capable of achieving. They have transcended the mortal plane and become a mythic hero.
I've been guilty of level inflation myself, and this is a serious gear shift for me. I'm going to have to reassess how my players fit into Alexandrian society.