Next BLU update, please increase the number of active action slots.

[Rongway]

Or, better yet, the devs should just lock what abilities could go in what slot so that you're forced to use different styles of skills, such as 3 defensive skills, 12 DPS skills, 5 healing skills, or some other arbitrary delineation and subtype.

Tangent: this is the only way blue mage could ever be converted to a real job and still be a blue mage. Have slots assigned to specific types of actions, unlock slots as you level up, and require all slots up to a duty's minimum level be filled appropriately to enter.