Mine is a game balance beef. Generally, I think the amount of resources one devotes to something should determine the benefit they gain from it. If you're reserving the option to attack (even at penalties), you're devoting less resources than if you give up all attacks to concentrate on being defensive.
As far as "realism" goes, it's D&D. I'm not sure how much benefit traditional martial arts are going to be versus a house-sized, fire-breathing lizard.
As far as "realism" goes, it's D&D. I'm not sure how much benefit traditional martial arts are going to be versus a house-sized, fire-breathing lizard.