So I added the Swiftfoot Boots and got the hexproof protection for the Tormented Soul. Having the soul be protected and equipped with the flail is very helpful. I also found Grand Abolisher and have decided that his protection from spells during the turn is excellent for preventing an unwanted tap before attacks begin with exalted fliers or souls.
The biggest element of defense though so far has got to be lifelink. By getting a Vault of the Archangel into play the swings from exalted allow you to play defense by recouping the life and absorbing the hits between turns. Since Exalted decks are such glass cannons you have to get defense from somewhere and there is only so much control/removal you can add. The lifelink also benefits from the fact that as exalted you must attack every single turn, even if the damage is not being delivered to the player and just his creatures.