Well, here's a large part of the problem:

Maneuvers, by their nature, are repeatable attacks, sometimes as often as every other round.

Epic spells, on the other hand, are one/day deals, sometimes slightly more often than that. They cost large amounts of time, money, and XP to create.

Thus, your maneuvers must always be weaker than the Epic Spells achievable at a similiar level...MUCH weaker.

I'd also suggest taking away the maneuver level, and replacing it with a minimum Martial Lore check to learn that specific maneuver. If there's a DC, treat the maneuver as being a 10th level maneuver, then homebrew feats to raise the DC (much like adding a DC to an Epic Spell).

When I get my new computer and get off of this temporary PoS, I may have some ideas of my own to add.