I actually enjoy playing at Epic level since at that level of game play it doesn't matter how much you optimize since the DM doesn't have to hold back because of the CR system. They can (and should) be giving you end of the world sequences on a daily basis.
I'd like to quote an old DM of mines that I had once upon a time
Even if you conquer the world in one day, that is just ONE world... Why conquer one when you can conquer them all? (replace Conquer with Save if you are Good or whatever).In your standard 1-20 campaign you are often fighting to save or conquer the world as a whole. At Epic level, that campaign becomes an adventuring day.
EHHHHH!!! It's always been a dream of mines to find a half decent WBL formula that can make everyone happy since I do agree with you that WBL is pretty borked for Mundanes who require MUCH more to play effective and Casters who require MUCH less to play effectively.