Sejs said:
Assuming you have access to the corpse of a creature with 20 racial HD at level 5
You just have to find the right graveyard ; )
Really though, animate dead can easily get out of hand, even if you only animate things your party kills.
Bah, that's not abuse, that's what wizards -do-. Wizards are all about planning ahead, knowing what you're getting into and loading up the appropriate spells.
A (for example) 14th level wizard could use mnenomic enhancer the day before an adventure to obtain an extra 20 3rd level spells (enough to say, give the whole party protection from every element, and still have a bunch of extra fireballs and such). You feel the writer's intended for this?
One dispel magic later and you're out the symbol and upwards of 4,000 exp that was invested in the permanancy. Hardly cost effective.
I typically use a ring of counter-spelling loaded with dispel magic, but even without, it can still be difficult to dispel something that has a decent caster level. And if the dispeller is high enough level to reliably dispel the symbol, I figure he could instead be using his action to cast nastier (save or die) spells on me anyways.
Other strategies to protect your investment:
1) Have a high level caster put a cheap 500xp permanent spell on you (it will be hit by an area dispel before your expensive one, saving it).
2) Spell-turning or rod of absorption should cancel out targeted dispels