Another thing to note is that every enemy in Ipsen's Castle except Tonberries and Gargoyles can be afflicted by Freeze (or Quina's Frost spell, and as said earlier, Gargoyles are easily killed with a Soft). So in short, either have Quina with the Frost spell or Steiner with the Ice Brand sword + Add Status and give them as high a Spirit as possible. Freeze + any physical attack with kill a monster instantly.