Skill Expressions for Dragoon

I'm afraid to say it doesn't necessarily work for all cases. It depends heavily on the skill's damage property (Physical/Magic) and what the class's base weapon is. Apparently, even if you don't have a weapon equipped, the skill's mana/cooldown is changed accordingly with the base weapon.

For the Magical subclasses: Dragoon and Impaler, it's fine to just unequip the weapon since the D. Lancer's base weapon is a Long Lance. However, when you get to the Physical Subclasses: Skirmisher and Vanguard, you need to use a Beam Spear for the weapon since all other weapons tend to skew data slightly.

This applies to all other classes as well. However, the one exception is the Thief class which has no weapon that reveals base mana cost/cooldown. In this case, it requires a little mathematics.