I know full well the anguish of meta-gaming, and so far the most successful cure I have personally found has been to look specifically for players disinterested in meta-gaming.
Following changes done
Lore of the Dead - Casting time changed to 2 rounds
Tales of the Skull - Added feats to the list of information gained. Decreases casting time to 2 rounds to make all of the spells have the same casting time at the lower levels. Should still be sufficient for the spell to be "akward" to use in combat.
Skull Drone - Made Dexterity and Natural Armor scores dependent on the size of the skull
Introduced the following new spells
Borrowed Mysteries - Allows the caster to temporary gain a number of feats from a skull
Sinister Lore - Allows the caster to permanently learn skills.
Crown of Skulls - Increases the casters Charisma, Intelligence or Wisdom