A hypothetical redesign of the black mage:
|1st||+0||+0||+0||+2||Archetype Power (Lesser), Spellcasting||5||4||-||-|
|2nd||+1||+0||+0||+3||Advanced Learning, Rebuke Undead||6||5||-||-|
|3rd||+1||+1||+1||+3||Archetype Power (Moderate)||6||6||3||-|
|4th||+2||+1||+1||+4||Advanced Learning, Fell Knowledge||6||6||4||-|
|6th||+3||+2||+2||+5||Advanced Learning, Archetype Power (Greater)||6||6||6||4|
Fiendish Familiar gets axed due to being overly powerful
Advanced Learning: the black mage may add one spell to his list of spells known. This spell may not be of a higher level than the highest level of spells the black mage is normally capable of casting. This spell may be from the conjuration or necromancy schools, and may be drawn from either the sorcerer/wizard or cleric spell lists.
This would assume core-only spell lists, allowing mage classes to access non-core choices with Advanced Learning. This would also allow two necromancers, for example, to differentiate themselves a little.
Another possibility for reining in mage classes: d4 HD and no armor proficiency.