Who are the prototype characters (fictional/historical) for the Warlord concept? Napoleon Bonaparte? Julius Caesar? Captain Kirk? The Doctor? The last of these is the only one who does anything resembling healing, and then not as often as the name suggests.
Based on what I've learned, what I consider examples of the Warlord:
Parson Gotti of
Erfworld (strategic and tactical planning; no fighting, no healing)
「BLANK」 from
No Game, No Life (strategic and tactical planning; no fighting, no healing)
Izaya from
Durarara!! (strategic and tactical planning, no fighting, no healing)
Shiroe from
Log Horizon (strategic and tactical planning, fighting, some healing)
Tanya from
The Saga of Tanya the Evil (strategic and tactical planning, fighting, inspiring)
The tactician from Suikoden (varied by version) (strategic and tactical planning; some fighting, no healing)
Each of the heroes from
Suikoden 3 (Hugo, Chris, Geddoe).
– Hugo gained followers partly by loyalty to him, partly because of loyalty to his mother. Leader of a cause. (fighter, minimal planning, no healing)
– Chris gained followers from being a respected commander. Leader of troops. (fighter, leader, healer)
– Geddoe gained followers that were mercenaries. Loyalty was to money, and the fact that no one questioned their past, but they also respected him. (fighter, planner, no healing)
Aside: Planning aspects are pushed aside in games, as the player is handling that, whereas they are emphasized in shows and stories that want to show off the protagonist's abilities. Explicit healing is almost never relevant, but being inspirational is common, in keeping people going when they were about to give up. Fighting is less relevant in shows/stories, and more relevant in games.
As far as nominal classes go: Parson is a magician of some sort, and Shiroe is explicitly a magician (Red Mage, a controller in D&D terms). Izaya and Geddoe would be Rogues (Mastermind subclass). Hugo and Chris would be Fighters (though Hugo could be considered a Barbarian). Tanya might be either a Fighter or a Ranger.
Basically, I can't really wrap my head around a Warlord who is not
also some other class. Either the Warlord has to have every other class as a subclass, or every other class has to have Warlord as a subclass. This also makes sense because the Warlord has to have a vector to apply its talents. Without that, it's just throwing around numbers, which might as well be magic, which might as well be a magic-based class. The only one that feels like it might be able to pull an exception is 「BLANK」, as they work on an almost purely strategic/tactical level, but even then I could see classifying them as Rogues (Insightful subclass).
Mostly, I see Warlord as a
quality that can be applied to a person, and thus not a class. A Warlord is not a thing unto itself. Generally a class describes a thing you do. A Warlord is saying, "I can do this thing I do to great advantage for me and my allies."
The problem is that many subclasses haven't been entirely built out to handle this factor. An Insightful Rogue can spot weaknesses, and thus fight better, but can't point out those weaknesses to others in the party. A Mastermind doesn't provide the inspiration to nudge people to fight a little bit longer. And it's those minor gaps that leave their utility as Warlord variants just a bit too lacking.
An entire separate class, however, would allow multiclassing to pick up those basic, missing elements. And maybe that would be a better design direction. It almost certainly won't be taken by WotC, but it's better than trying to duplicate every other regular class as a subclass of the Warlord. Just create a class whose primary purpose it for multiclassing, providing some of the missing elements that the almost-Warlord subclasses need.