Dragoons are kinda an odd class, and they probably could use a subtle Buff. Thier magic defense is indeed pretty low, not so low that the class is unplayable, but Dragoons need to be a lot more careful to avoid damage than monks. This is somewhat glaring, as thier toolset suggests that they are supposed to be a sort of Tank-lite.
Second, thier base non burst damage is dramatically inferior to monks. Thier burst is amazing, but takes a fair degree of skill to fully utilize, and doesn't fully compensate for the lower base-line, especially in longer fights.
Basically, DRG needs slightly higher defense, and the potency of its basic rotation could use a subtle Buff.
Nothing major though, Dragoon isn't a fundamentally broken class, it just needs balancing.