(I can actually explain why Dragon element is weak to Dragon Element. D. Element, like Noctinogi mentioned to me in pms, is an Absorption or draining element. When a Draining element tries to Drain another one, they cancel eachother out. I believe this creates a Feedback effect similar to an implosion, this also explains why D. Element tends to be less effective to water and Ice element monsters which generate less energy than Fire and Lighting ones. As the D. Element has less energy to absorb with the former and more so to the Latter.)