Under-rated Cleric Domains
The magic domain provides Mage Armor early on, now if people have noticed it stacks with nearly every other armor boost, and you can caste it on someone in normal armor and still get the full bonus. In fact I have been tempted to start picking up Bracers of Armor for my non-casters.
Example Armor Class with no magical items at 8th level (Rare but as an example)
Breast Plate, Large Shield = 10
Magic Vestment +2/+2 on Armor and Shield, Mage Armor +4
Armor Class = 28 if you have Dexterity 16 after buffs, this should give you a 70% chance to be missed by equivalent level fighters (8 BAB + 1 WF, 18 STR = +13 to hit) It would be really easy to improve this as to be even higher.
Fire Domain, ok now I know that alot of people say that Water or Air is strictly better but why Fire Ball > Call Lightning, Empowered Fire ball > Ice Storm (but this is close), Maximized Fire Ball > Chain Lightning.
However there is an argument to be made that in the OC, fire damage is resisted more often so your mileage may be different.
Now Combine the two, I will use 9th level as the standard. . .
Armor Class: 28 minimum, without bark skin or natural armor amulet
level 1 = Mage Armor
level 2 = Melf's Acid Arrows
level 3 = Fire Ball
level 4 = Extended Magic Vestments (+ silent fire balls if you want to be a bastard)
level 5 = empowered fireballs