Give Runecasters higher defenses against magical attacks
Runecasters can't defend themselves against magical attacks. A class whose purpose is mastery of magic, and they have no clue how to protect themselves against it? It doesn't make sense.
Rite of Abjuration is also worthless given that it costs a Major action and you are virtually always better off attacking with said action instead.
AdminNick (Manager, 10x10 Room) commented
Rite of Abjuration proactively does this by making a foe less effective at using magic. That said, it's likely you'll see more Lore-based abilities in the future which do what you are describing.