DNecro8/favored soul4/Mystic Theurge
Pratictised caster (DN) to make sure you won't hurt you spell casting.
Now you can have a true horde of undead (summon undead doesn't count for your limit). The weak ones are meant to be killed (destruction retribution and unliving weapon).
Use your favored soul spells to buff and summon and your DN spells to kill.
Seems good, I'll try it someday.