I have no doubt that you can achieve a balanced game at epic levels in 3.x. I have some thoughts on that which I may or may not get to at a later time. However, [MENTION=17106]Ahnehnois[/MENTION], I am curious about the makeup of your 37th-level characters. Could you give an example of what a typical 'mundane' and 'magical' character looks like in your campaign?
Epic level play is not exactly the middle of the road and I haven't done it in a while.
However, I was using an example of a character who was a half-dragon but otherwise a straight fighter IIRC. He probably started with around a modifier total of 11 for his ability scores, and probably had the maximum allowable inherent bonus in any that he cared about. I know he had an artifact sword with spectacular powers and some kind of smite ability (which I think is what killed the dragon). I would guess he had multiple additional artifact-level magic items, which may or may not have been relevant in the scenario I described. For me, an artifact magic item not only includes epic-level numerical bonuses, but some special power that violates conventional limits (an untyped bonus for example, or the ability to reroll or otherwise change the paradigm of a d20 roll, or some open-ended wishlike power). I'm sure the character also had an array of feats cherry-picked from all available sources, and probably over a million gp in nonartifact epic magic items. The player still uses the character's name as his message board avatar.
Another character I recall being in that party was a blind wizard, who had some kind of blindsight ability that I can't recall how he got, and I think was human and straight wizards up to 37 or so. As this was a new character (whereas the fighter had been played at earlier levels) I suspect the weight of his gear was marginally less. However, I'm sure he also had multiple limit-breaking artifacts, and probably the same ability scores and gp. He had a virtually limitless allotment of spells as characters of that level do. I'm sure he had some custom-designed epic spells (I like the epic spell system, though it requires a lot of adjudication). His blindsight may have been useful in targeting the dragon; I don't recall. However, the thought of him doing any direct or indirect harm to it was pretty unlikely.
My point would be that by having made it to 37th level, a character is pretty clearly not typical. If a character advances through play to that level, some pretty special things are accumulated in the process. If a character is created for that level, I assume a certain Darwinian aspect and treat the character as being super special. I'm not sure how a standard array, single-classed human with only garden-variety treasure fares in the wizard 37 vs fighter 37 comparison, but I don't think that's a reasonable comparison regardless.
To a lesser extent, I think the same logic applies to high-level play within the core rules. I don't assume that any wizard that made it to double-digit levels started with 15 Int, nor a fighter with 15 Str. High level is not an assumed part of a typical adventurer's career; high level characters are special.
