A Modular Approach to Solving High Level Game Woes

[S'mon]

The best approach is to scale everything bad to old edition power levels; a balor is a 12th level threat and not the 20th level blashempy-spamming monster that 3.5e made it out to be.

Besides, the 12th+ level mechanics were always poorly considered(remember, the highest level PC in the Greyhawk campaign was 12th? 14th? level).

I agree that this is the best approach to 3e, and the one I follow. The only significant issue is that 1e allowed for 18th level NPCs as foes in a world where 10th level PCs could kill Lolth. 3e does not, due to the power gradient, so if the PCs top out at 10th the NPCs need to, also.