Darrin's post on the Dragon Compendium version (you seem to have went with interpretation number two). What happens when one twin is affected by a maze spell and the other isn't, for example? Wonkiness abounds.
Also, I'm afraid that I disagree with the Wisdom penalty. The fluff presented in the Dragon Compendium has them as patient, peace-loving philosophers in pursuit of true understanding. It sets them up to be Monks so hard that (despite a favored class of Bard ) their god's holy symbol is a yin-yang.
Sorry to be such a downer. I just really love the idea of the Dvati (one soul, two bodies, not the specific society fluff) and haven't been able to get them to work right, mechanically.