Say, theoretically, you were against Divine Healing. You wouldn't have to ban the Cleric, just the specific cleric spells that healed. So, as long as the Warlord is not substantially less flexible and customizable than existing support classes, it's a non-issue.
Just a nitpick, there's no such thing as "divine healing" anymore. Divine, arcane, and the like don't carry nearly the same weight, really only applying to spellcasting focus.
However, if you did have a problem with spell based hit point recovery, removing cure wounds wouldn't solve the problem. Neither would banning the cleric or the paladin. Because there are numerous monsters that use spell based hp recovery. It's just part of the rules.
The argument that martial healing would be limited to the warlord assumes it would not spread. Which is problematic. If the game begins assuming that hit points are morale based as a default that will affect everyone's game as other subclasses, monsters, or elements of an adventure will assume this as well. In such a system it's easy to imagine a module author including an NPC that gives an inspiring speech during a climactic battle restoring hp, even if said NPC isn't explicitly a warlord.
The problem is in the mechanic, not just the class that typically uses the mechanic. It's like the Damage on a Miss debate during the playtest. Saying "you can just ban that fighter option" simply does not work because the mechanic is still seen as a valid mechanic, and can spreads to other places, like the playtest stone giant.
Those aren't exactly contrary goals. The 4e Warlord was modestly customizable, and could be used to make the 'lazy' fan-build as will as the half-dozen official builds. 4e worked within much tighter design parameters, so a 5e version could easily embrace all that, and more. Again, no problem. In fact, a great deal of opportunity, as there is vast, under-utilized design space available for martial characters (which, currently, are all DPR-focused).
This assumes the goal is to build a 5e class to be compatible with 4e design goals, rather than looking at the concept of the class divorced from its mechanical implementation and designing the class around that. Using the source material as inspiration, rather than a checklist that needs to be filled. And looking at what the class should be doing and implementing new mechanics that replicate the narrative effect rather than copying past design.
It also assumes they're updating the full length and breadth of the warlord class that was created over the entire edition (including fan builds and Dragon) rather than just updating the class based on its presentation in the PHB1. It's not like class options from every splatbook were considered for every class updated to 5e.
This is nonsense on two levels. 1) 5e is built on the idea of DM Empowerment, it gives many optional rules, from Feats & MCing right in the PH, to multiple modules in the DMG, plus that free supplement, plus UA - and which module or optional rules are available is entirely in the DM's domain. 2) If you don't like saying no to /a/ player, where do you get off trying to say 'no' to /every/ player? That's like trying to dictate to everyone how they play the game. It's contrary to the spirit in which 5e was conceived and has no place in a 5e discussion.
I don't disagree. But that still doesn't make saying "no" easy to do or desirable..
Just because the DM can say "no" doesn't mean designers should set out to generate situations where DMs have to say "no". Saying "no" is a choice and the game shouldn't set out to force DMs to make that choice.
Just look at the fuss over the aarakocra. And that was a race that occupied a third of the page space of a class and likely took a tenth of the time to test and develop. And it wasn't even in a "real" book.
Class and race options should be options the game assumes the majority of people will allow. So saying "no" to those options should be rare.
Conversely, rules modules should be the opposite, and assume people aren't going to use them, but these require less playtesting and development time (if they even need playtesting at all).
And when you say "no" to an option as a DM, it should preferably be because the story option does not fit. Wizards are banned because magic is different. Clerics are banned because the gods are dead. The only races are humans, elves, and dwarves because the setting is inspired by Norse lore. When you start banning things because "mechanic X doesn't work" that usually mean an option is broken or is not working. And that's a problem.
You have no idea how many people constitute a 'LOT,' and have no statistics to back that up. At best, you've made a fallacious appeal to (un)popularlity, at worst, again, you're trying to dictate to everyone how they play the game.
I can make an informed guess.
I know that every player tends to have maybe two or three favourite classes. So any new class options - let alone an entirely new class - will always appeal to only a small fraction of the audience.
But that's not all.
I know that every poll on ENWorld shows an even split between pro and con warlord factions.
I know that the majority of ENWorlders do not post in said polls, and thus have no strong feelings (or they would vote).
I know that ENWorld is non-representative and constitutes a minority of gamers, being the more dedicated (read: obsessive) fans. And that the majority of gamers are casual and likely do not have strong opinions of any class.
I know that 5e is bringing back fans that skipped 4e, and thus do not have strong feels regarding anything in that edition including the warlord. And fans that did not like 4e, and are unlikely to have positive feelings regarding 4e.
It's pretty safe to say that the warlord is a fringe class. Period.
Then add to this the fact that warlord fans are deeply divided and any attempt to make a warlord class will likely alienate half it's already fractional audience. And that's a LOT of work to appease a VERY small number of people.
Just look at the massive number of warlord fan classes. Most of which are greeted by apathy or complaints. I don't see how an official class would be received any differently.
Actually, banning the class, or even banning the specific abilities you find objectionable /does/ change that for your campaign, which is the only campaign you have any business making that kind of decision for. Again, you presume the right to dictate to everyone how they play the game.
That's not what I said or claimed. That's not even remotely close to the point I was making.
I'm not trying to dictate how everyone plays the game. I want the game to be neutral on the dictates of mechanics to allow people to play the game how they want.
When a class or mechanic (that is not contained in an optional rules module) changes the game it is an issue.