In AD&D, there was a specific intent that the play style would change from individually going out to solve problems below 10th level into ruling groups and bringing comrades along above 10th level. There was a reason that most characters got followers around that time, and why HP switched from dice rolls into flat +2HP/level at that point.

I'd think that part of the reason it is something which happens across most/all systems of D&D has to do with a few things. PCs are at a greater risk of dying at lower levels. The orc with a 2d6 greataxe is a much greater threat to a 24 HP fighter or even a 40 HP fighter than to a 217 HP wizard. Magic is less common and less abundant so even something as simple as climbing a cliff needs to be resolved with something more than "just cast Fly on all party members". Equipment and expenses are more restricted as well, to the point where PCs don't just have dozens of potions and personalize magical equipment and so on.

Once you get to a certain level, common threats start becoming trivial which means the game needs to shift gears. Either you change the direction the game goes in - by having the PCs become landowners and managing groups, for example - or you just increase the numbers and start throwing ludicrous numbers at the party.

I think that some editions of D&D were intended to do this, it was just never officially written down and so got a bit mangled in later editions. Like I said, it seems like AD&D intended players to retire or at least deligate, which is why they got followers and why spellcasters had long-range mass teleport spells or Mordenkainen's Magnificent Mansion housing dozens of people. Later designers didn't take the change in theme into account, hence D&D3e's Leadership feat and some spells seemingly out of place for a small adventuring party.

Quote Originally Posted by Yora View Post
So you're argument is that wizard (and to some extend cleric) spells are not too strong but primarily too diverse?

Interesting thought. Sounds quite convincing to me, actually.
I'd say that both numbers and spells are causing the problem. It's not just that a wizard could cast Fly and Invisibility and just float around summoning anything they like as much as they want. It's that a high level wizard simply cannot be meaningfully hurt by a low level threat. The orc with the greataxe can only do 15 damage, maximum, with an attack. When the wizard could easily have 100, 200, or over 500 HP, that kind of damage is a joke, even if it didn't miss 95% of the time.

But yes, the spell lists are causing a big part of the problem. Everybody is so focused on reproducing earlier editions with their spell lists that they don't focus on which spells are good to keep and which ones can be avoided or dropped - or, for that matter, how to change casting and spell designs to fit a particular theme.