Even though I've enjoyed playing heavily armored clerics in every edition, I always felt that the class didn't really reflect what it purports to.
I voted "No, that's why we have Paladins" but that's not entirely accurate, either. To me, it was less about their defense and a bit more about their ability to land a blow.
The Paladin was inspired by the paladins of lore and legend- people personally chosen by a divine force to be warriors to take up arms in that force's name. As such, they should be fully armed and armored warriors with a hint of divine energy.
The heavily armored cleric, OTOH, was supposed to model the armed priests and monks of the knightly orders of the Crusades and other periods. However, those people were usually well-trained warriors first, who took Holy Orders before they entered the field. Their priestly training was, in most cases, rather...lax.
Not that there weren't true men of the cloth out there banging heads. They just generally weren't very good at it. And, but for a very few, they didn't have the heavy armor of the knights- most orders wouldn't permit such an expenditure of money- unless they got it through non-Church sources (it was theirs before they became priests, it was donated, it was captured, etc.).
IMHO, the clerical class should have had simple weapons, Medium armor at best, and a poor BAB, to use 3Ed terms, and modeling the medieval warrior priest would have remained the result of multiclassing Cleric and Fighters.