I loved the idea behind the system... but yeah- it becomes difficult to do anything with it.
Someone on these boards created a system... legendary spells- something like that, that I liked a lot. Used the basic epic rules but expanded upon them and made it all more workable.
There are a few different versions floating around... The legendary spell system is mine and it's in the Downloads section. I'm also working on a newer, simpler version, which is in the House Rules forum (a couple pages back).
And the feat does sound rather over-powered.
Animate dead is Clr 3, Sor/Wiz 4, but this feat is a +3 modifier, which effectively makes any spell cast with it L4. You're also adding another spell effect, but the animation only works if the target is killed, so it's about right. It's a little weird, but I don't think it's too overpowered.
Epic spells are generally only worthwhile if you're abusing them by making super long duration buffs that take a while to cast or something.
Epic spells are... not for combat situations, unless you're particularly deep into epic, and are okay with 100d6 backlash damage to Destroy your opponent with a 100d20 attack.....
Epic spells are
supposed to be able to do really cool huge effects like create flying castles, make you immortal, or slay everyone in a small town and raise them as wights under the caster's control*. Unfortunately, the way they implemented the rules, most of these effects are impossible.
*This is just IMO. I don't know about you guys, but when I think of epic magic, I don't think of just another bunch of 0-9th level spells that do the same thing, but better. That's what seriously disappointed me about the magic items, too - just bigger, badder, and better.
And while I'm on the subject, going with a skill-based system was the stupidest thing they could have done. Making it skill-based throws all thoughts of balance out the window from the get-go, because all of a sudden it becomes a race to see who can get the highest skill total so they can cast the most powerful spells. You add in the mitigation system, and it gets even worse - we've all seen the DC 0 spells with huge rituals, XP costs, and/or backlash. There are no built-in limits to the system, and loopholes large enough to drive a truck through.
The Exodus epic level arena has a house-rule to that effect that you might enjoy; things scale without quite the sudden jump of the *10 Epic modifier:
I like this. Course, if WotC had actually thought to fix the gold progression, we might not have to rely on multipliers, but this works.
Even very basic magical effects require ridiculous Spellcraft DCs to pull off. These DCs often go into the hundreds, which is beyond all sanity. Who has ever seriously played a 200th level character?
Some of the higher-end spells (vengeful gaze of god, e.g.) were "examples of how far you could take the system". I can't recall where I heard that, but there you go. They weren't actually intended to be castable - they were just included to show off how broken the system really is.