Clerics are Holy Warriors. They are also other things, depending upon your particular flavor, but Holy Warrior is one. Paladins are Holy Warriors. What then, lore-wise, is the difference? They both fulfill the same function in the campaign world.
I'm not sure why you feel that clerics are primarily warriors. Would you call the bladesinger an "arcane warrior" rather than a "warrior mage" just because he has proficiency in a martial weapon and armor?
I think people are getting hung up on the heavy armor proficiency. Armor "proficiency" really only appeared in 3e. In prior editions, they just said what armors someone could or couldn't wear. If you look at the way allowed armors actually were assigned, it was basically that you could wear whatever armor didn't interfere with your class abilities (even though sometimes that was retroactive justification).
-Wizards couldn't wear armor at all because it messed with spellcasting.
-Thieves had to stick to lighter armor because heavier armor interfered with being sneaky, acrobatic, and exercising fine manual dexterity.
-Clerics couldn't...oh wait. Armor doesn't really get in the way of any cleric abilities. So they were allowed to wear full armor.
After enough years of people saying, "but what happens if they
do put on armor..."* 3e just said, "Okay, look, they aren't trained, so they suffer these penalties. Now that you know that, you're never going to wear armor that you aren't supposed to anyway, just like before we made up rules for it. You're welcome."
Other than some contradictory (and contradicted) fluff, clerics have never primarily been warriors. They have been casters.
Holy Magic-Users, if you want to define them in terms of other classes.
So why do I keep bringing up this "primarily" crap, someone is probably thinking. Well, because that's how nouns and adjectives work in English. A
holy warrior is a warrior who is holy. A
warrior priest is a priest who fights. These are significantly different. (Again, if you need mechanics to back it up, it's the difference between d10 and d8 hit points, and more favorable vs. less favorable attack bonus, as well as the vast difference in spell-casting.)
If someone wants to make the argument that clerics were traditionally warrior priests, then I won't argue with it. But they have always been shown as primarily priests, with warrior tacked on in some editions in some situations.
In 2e the relevant class groupings were:
Warrior
-Fighter
-Paladin
-Ranger
Priest
-Cleric
-Priest of a specific mythos (druid is an example)
Cleric is explicitly
not primarily a warrior, while paladin explicitly is. 2e went further by making those specific mythos very broad so that some clerics are warrior priests, while others have nothing to do with that archetype at all.
And again, if you actually look at any adventure or campaign sourcebook from at least 2e (and plenty of 1e too) through 3e, pretty much every single NPC priest or acolyte has been a member of the cleric class.**
And also, for four editions running we've had direct support for the heavy-armor wearing, sword-wielding and shield-carrying and infidel-smiting kind of Cleric, and for four editions running we've had the question of what exactly is a Paladin's place in the lore of things with that kind of Cleric out there.
And I would submit that we've primarily had that problem because of people not understanding or being familiar with the information I presented in the last few paragraphs. 2e is not an edition to be skipped if you want good understanding of the evolution of classes in D&D. I've never heard of this issue from anyone with solid 2e exposure, because, notwithstanding the contradictory relic text in the PHB "Cleric" entry, 2e otherwise consistently and unambiguously presents the cleric as priest, paladin as warrior assumption with clarity throughout the edition. (In fact, perhaps this is the reason for my odd intolerance, since I consider 2e to be the high point of D&D lore and fluff.)
The priest and acolyte in the MM are spellcasters--clerics--because those are the only type that need their own stat block. A non-spellcasting priest is a commoner or noble with the Religion skill added.
This is actually a perfectly reasonable way to reconcile the current mechanics if you want to go that way. It's not how I'd do it for a couple of reasons, but it works as well as can be expected.
And no, most priests in Eberron--like most priests in most other settings--are just people in the Church hierarchy. Actual spellcasting clerics are the minority.
Thanks for the clarification on Eberron. I've never had the Eberron books so I had to look up some information online. From what I can tell though, Eberron seems to have been the
origin of the idea of clerics being a minority with religious hierarchies rather than the standard. Before Eberron (and outside of Eberron, even in 3e) it simply wasn't the case. Pick up any non-Eberron adventure or campaign supplement published by TSR or WotC prior to 4e, find an NPC priest, and you'll see "X-level cleric" at the start of their stats. This isn't just for the villains and major players, this is for every village priest and acolyte in every dinky little temple or shrine.
And 2e made no apologies for it in its class divisions (and from what others have said, apparently the class was originally named Priest rather than cleric anyway--though this isn't directly relevant to this specific point).
But it
is a valid question as to why everyone in the priestly profession gets to be a full-blown X-level character, while most people were just 0-level NPCs, or "normal man" etc. The same concern can apply to criminals. How come every member of a thieves' guild actually gets to be an X-level thief (or rogue)?
The answer is that, messy as it is, they decided that those classes represented those character archetypes in the world, period.
Now, one can handle this a variety of ways. You can say, "forget that" and just make most people commoners with classes entirely reserved for PCs, important NPCs, etc. Or you can take 5e's approach and use NPC monster entries for priests and acolytes and assassins and such that more or less represent and do similar things to PC classes, just simplified and prepackaged for quicker microwave preparation. Or you can go more old-school, and make every priest and pick pocket a full-fledged X-level cleric or rogue.
Anyone can find whatever method works best for them. But in D&D tradition, clerics have been primarily priests (and casters) since the beginning. "Warrior priest" has been sometimes assumed, sometimes optional, but never primary. Paladins by contrast have
always been warriors first and foremost, with some form of holy power always there. They've never been represented as priests, warrior or otherwise.
I'm not seeing any problem with how it fits into actual use in a campaign, other than by, for some reason, objecting to the way they've actually been presented. Priests of some deities are warrior priests. When they aren't running the church, they go out and stab things and scream battle cries in Thor's name. That doesn't step on the toes of the paladin as a knight in shining armor***, unless you are trying to look at things from purely mechanical standpoint of "hit monster with weapon, do damage". And yet, that doesn't even work, because clerics have lots of spellcasting, and paladins have always been highly limited compared to clerics. (And as I mentioned at the beginning of the post, wielding a weapon and wearing armor does not a (D&D) "warrior" make.)
* To be clear, I do think this was a perfectly reasonable question.
** Eberron being a noted exception.
*** There isn't even a problem with more recent presentations of paladins, including 5e, because they just take the idea of holy warrior and expand it beyond the knight in shining armor.