Was thinking about how people find some of the card effects pretty "meh" or too situational in a lot of cases. Without adding more cards, or even touching the existing cards, I think an interesting way to handle this would be to make them omni-targetable...Ally and Enemy.

Ideally, each card would have a positive and negative effect, depending on who it was cast on. Think Tarot cards with their "Reverse"/upside-down meanings, and have them apply a pseudo-mirror effect when cast on an enemy.

Card = Ally Effect/Enemy Effect
Balance = Damage Up/Damage Down
Ewer = Mana Refresh/INT Down
Spire = TP Refresh/STR Down
Bole = Defense Up/Increased Damage Taken
Spear = CD Down/Silence
Arrow = Speed Up/Slow+Heavy

That way, every card has a good use in most situations. Only one I can see a real issue with balance-wise might be Balance and Bole potentially. Honestly, Balance should do 5% damage down and Disable should be buffed a bit personally.