Bias aside, Dragoons are specialized to kill dragons only. Their spiky armor is meant to dig deep through the scales of a dragon, so when a Dragoon dives on top of a Dragon's back, they aren't just shrugged off with a single barrel roll. At any rate, they're mainly specialized against one type of foe only and spend the majority of their training against killing dragons. Even in the Lv52 quest, one high ranking DRG is astounded at how you fight because the way the WoL fights as a DRG is different from other DRGs (probably a subtle reference at our Lancer skills which are Gridanian in nature, not Ishgardian, and possibly our Marauder and Pugilist skills which are needed to unlock DRG). tl;dr DRG are extremely powerful, but only against Dragons which they spend their lives training for, and not really any other type of creature.