Yes, surging wave is devastating for defense ability. Surging wave can slam a creature. If the creature is slammed, it is incapacitated. Incapacitated creatures cannot make a defense roll (with a couple of exceptions). Essentially incapacitated is a special case stun condition.
The exceptions relate to autonomous defenses such as dancing scimitar, and perhaps the enchantment defenses (force orb/sword). The dancing scimitar is autonomous which means it can still roll a defense for you if you are incapacitated because it is not affected by the condition. It acts for you. The enchantments I would have to check to be sure if those also count as autonomous or not. If they are, then they could also be available if the creature enchanted becomes stunned in some way.