I know about the mystic theruge - I need another prc that levels both divine and arcane and is preferably good, but I can't seem to find one other than the necromancer or whatever. If one exists I don't know about someone lemme know.
hmm if this is all your asking your question would probably belong on the question answer topic.
have you thought of fochlucian (or something) lyrist it provides both arcane and divine progression within the bard and druid flavour.
if i remember correctly it is in the complete adventurer.
but remember the next time you have a short question just post it on simple question simple answer topic.
There is also arcane hierophant from Races of the Wild. You can get trackless step from holt warden (Complete Champion).
Fochlucan lyrist would not be that food, unless you find a way to gain evasion without wasting a level.
But why would you want that? Epic divine and arcane spells can be achieved even with 21st Level and only need a minimum on knowledge ranks so... Why care so much?
There isn't much to achieve for Epic Casters other than more Spell Slots through feats or epic spells... and caster level but that could be increased easier...
3 levels of Holt Warden is awesome when combine with Archivist and Mystic Theurge.
Allows you to do an int focus
Gives you trackless step for Arcane Hierophant while still progressing your divine side
Gives you domain slots even though Archivist can't normally get domain slots.
If you go archivist see if you can squeeze in a level of sacred exorcist. That gives you turn undead(or rebuke) which you can use to fuel divine metamagic.