Can you treat disease with a first aid kit? Bandages, gauze, pain killers, tape and the like? What in the kit works against disease? Okay, disinfectant prevents infection from a wound, but it's not going to do squat against something you've ingested or come into contact with through the air.
The answer is "no more than I could reliably stabilize someone suffering from a potentially fatal wound."
That goes double in the middle of a combat.
It's stretching to say that would be able to treat disease or remove a physical condition. It had one use: stabilize the dying. Anything else is a house rule.
One of the two diseases listed in the DMG is treatable with a rare flower processed by a herbalism kit. So there's some precedent for non-magical treatment of disease. It's just so patchy it's like disease in general was an afterthought, and the overlap between healer's kits, the medicine skill and herbalism skill is just wierd, which is what you expect from an afterthought.
Still, that's only a way to negate the penalty at the cost of your entire action. There's still no way to actually remove it. The warlord has to spent their entire turn every turn keeping an allying fighting remotely normally. Oh, and the character still automatically fails any ability check related to sight. So that sucks.
I think we're talking at cross purposes here - my point is that new battlemaster maneuvers could be created that could fill these niches (ie - "Coordinated targetting - spend a superiority die to negate disadvantage for one ally/advantage against one ally as long as you are not suffering from the same effect, duration:concentration or 1 minute"). Not as effective as curing the condition, but possibly broader in application.
Bringing people back from near death is more Hollywood realism that still doesn't translate well. Just because you have dragons doesn't mean all the rules of reality and physics go out the window. It's not a "get out of logic free" card. The magic is cool and interesting because it's the exception to reality.
Bringing people back from near death is such a mundane event that a large number of public sites have a machine that will allow a layperson to do it. This isn't fantasy.
Letting a non-magical individual do it in a fantasy game is not that big of a stretch.
A theoretical warlord might have an ability that let them bring someone back who was dead for a few rounds, but any longer and that steps on paladin toes (and creates a free version of a spell that costs 300gp).
I don't give a crap about 'stepping on toes', especially since I'm arguing with someone who's saying I'm in a completely nonmagical party. You might be right about the free version of an expensive spell - but that's a balancing issue, not a fundamental flaw with the idea.
But, really, if the warlord can get to the character that quickly, why weren't they healing them earlier? That's the problem. People die when you have a healer because they're out of healing, the healer was out of commission, or something like a coup de grace or massive damage happened.
If we stick to revivify, it's a minute. And people die because in combat healing cannot keep up with in combat damage.
Let's see, in 3rd Edition remove paralysis and remove blindness/deafness were cleric/ paladin spells, remove disease was cleric/druid/ranger, remove fear was cleric/bard, and neutralize poison was bard/cleric/druid/ranger/paladin. Only remove curse had different classes, being bard/cleric/paladin/sorcerer/wizard. Oh, and stone to flesh was a wizard/sorcerer spell.
You missed break enchantment, which was the "everyone can potentially get rid of almost anything of 5th level or lower" spell available to almost everyone. Disease and poison were treatable by skill checks, fear is a temporary thing anyway (and would be well within the bailiwick of mundane dispelling I would think).
So big improvement for 5e over past editions by making three classes equally adept at filling the healer role, and allowing two others to do half the removal and be adequate back-up healers. I don't see it being necessary to include the restoration or cure wound spells on the wizard and sorcerer spell lists.
No, I'd much rather see other wizardly abilities to mitigate party damage. Hello Mr abjuration specialist! I think stone to flesh is a perfect example, especially since it used to come free with learning flesh to stone, and like you point out had some interesting utility uses. I seem to remember at one stage false life didn't have a self-only target too? I could be wrong of course...
But, again, the catch is that any class designed to fill the roll of the bard/druid/cleric should have access to those spells or comparable abilities. Otherwise they cannot fully do their role. It's like making a tank with d6 hit points; yeah, you might have the high AC but you can't stand up to many attacks. Relying on other classes to use those spells doesn't work, since that means the class isn't filling its role. That's like the fighter relying on the rogue for some damage mitigation or the evoker wizard requiring the ranger to keep their damage high.
Teamwork isn't a curse word. And the fighter should be relying on the entire party for damage mitigation - otherwise every monster in the fight is targeting one guy, and he's not getting any healing...
Especially since, half the classes in the game don't get the spells. If you're a party with a warlord and three other characters pulled from the list of barbarian, fighter, monk, rogue, wizard, sorcerer, warlock (or even a bard that doesn't take those spells) and someone gets diseased or blinded then the warlord isn't going to be able to help. They have to stop adventuring and go find a temple or roll up a new character.
Which is sort of my point - it shouldn't be that way, and it really doesn't have to be unless you're unwilling to say that in a world where we have examples of non-magical fantastical things, that anything a martial character does cannot be fantastic.
A new save would be good. But it's super easy to fail a save even with advantage. And that'd be a great warlord power.
Not sure what your trailing off sentence was, but allowing extra attempts to 'shake it off' seems on a par with hoping that the cleric has prepared the right spell today.
"Shake it off - as an action you may spend a superiority die to allow an ally to reattempt a save against a condition or effect that currently affects them. They may add the superiority die to their save result. The save is against the original DC of the effect."
But if we're accepting a warlord that's not quite a full healer - if we have to accept one that is "close enough" but cannot do everything - that can also apply to things like not easily getting unconscious creatures back in the fight. Or using temporary hit points instead of restoring health. Because they're not replacements for a cleric/druid/bard but their own class entirely, in the same way a warlock can kinda replace a wizard but not in every way and a ranger or bard can kinda replace a rogue but not in every way. We can worry less about fitting some arbitrary "role" that doesn't *really* exist as a design space in the game and focus on making a warlord that is really good at doing warlordy things rather than a warlord that is really good at doing clerical things.
Personally I would rather create a viable party. I think that does include getting unconscious people back on their feet, and I see that as being something that should be possible without magic.
Further, I think that with an expanded maneuvers system, the battlemaster is the class to do it.
