FWIW, even though I think D&D is basically a 10-level game, I think there's room for 3 "tiers," still.
There's the "mundane" tier when your fighter is just some squire and your wizard is just some apprentice, and you fight goblins and orcs like each one could kill seven of you.
There's the "heroic" tier, when your fighter is a celebrated warrior-king and your wizard is a talented spellcaster, and you can kill a hoarde of orcs, and slay a few dragons.
There's the "epic" tier, when your fighter can arm-wrestle Hercules, your Wizard can tear the fabric of reality asunder, and you can kill or become gods.
I don't think these tiers correspond directly to "levels," though they do correspond roughly to ranks of power. Each tier can have 10 levels each, or you can spread them out in about 3 levels per. I think different campaigns will find happiness in different tiers of play, others would want the whole sweep, and that is As It Should Be.
BEMCI, baby. This was a good idea ahead of its time.
