i parts of the healer role was disassociated from the leader role. So unless you lacked a ritual caster of any stripe, they were filled. They aren't in 5e.
Just had to use the 'D-word?' ;P
Seriously, though, spells that are meant to be cast out of combat, and/or can be cast as rituals are on another level of contribution than the sort 5e expects from martial characters. They just aren't a relevant concern. And, if the Warlord were making such contributions, its detractors would be just as vocal in decrying that, as you are in pretending it /must/ make those contributions. I see the catch-22 you're trying to construct, here, and it's invalid. There are no formal roles in 5e, any Warlord class can be designed to be an effective Warlord, true to the concept as it originally appeared prior to 5e, it doesn't have to be exactly like a Cleric to do that, nor, conversely, need it respect any sort of niche protection the Cleric may have enjoyed.
My point: if we want a full on warlord that can match a spellcaster point for point, perhaps something akin to the Martial Adepts might be a way to do it.
Martials never matched casters point-for-point, even in 4e, when they were best-balanced and nearest to resource parity. A 5e warlord needn't be balanced with casters anymore than it need be balanced with the Fighter. It just needs to be true to, and effective in, it's traditional role (not formal Role). That means, no, it needn't be raising the dead, and yes, it had better be restoring hps in combat.
Like most of these threads, everyone is full of ideas but almost no one actually bothers to write a build or put their time where their mouth is. And the few people that do write something are criticized because it doesn't meet some unrealistic standard or being the warlord that varies from person to person.
The Warlord, unlike most other classes we discuss around here, has a very clear, definitive vision, since it's only appeared once. It's a stark contrast to the psionics discussions, for instance, where each edition had a very different take.
They're just an excuse to argue and I think I'm done...
Promises, promises.
...
Getting back to the topic....
Let me take a crack at this too. I whould want to avoid making the abilities feel too much like magic because your not magic.
1) an at will ability to give people a small ammout of temporary HP. It would be their healing ability. A actual heal would feel too much like magic to me, and doing temporary HP gives the class a kind of pre planing focus that makes sense for a commander. Your the one making the plans.
Temp hps can't bring up a fallen comrade, so fail if they're the only option. The Warlord really need the ability to do both: grant temp hps in preparation, or restore hps (and grant extra saves) to bring an ally back into the fight.
2) An ambush ability that you can use in between battles to give your friends a bonus action at the start of the battle. Maybe based around so many actions to distribute rather then one action per member. (You know so you can't abuse this system by having armies of followers.)
Considering surprise grants you a full round (which could include bonus actions, anyway), I'm not so sure about that. Layered on top of surprise it could be superfluous or overpowered (or even both).
3) What if the warlord had a training ability. Like the ability to instruct someone in combat so they gain a weapon proficiency. I don't think the ability would be that powerful, but it could make a nice ribbon.
Training or drilling with a weapon or a specific maneuver or tactic could be an interesting trick. Like, 'here, use my proficiency bonus instead of your own,' in the next fight, while the Warlord is there & conscious.
4) Give them expertise dice and then the ability to pass the dice to someone else to use in their attack or keep for themselves. I would be a simple ability.
Sounds like one way to handle the 'training' idea.
....
There's another idea I saw in passing that just might work for a Warlord as a Fighter sub-class, it'd be about as satisfying as a Psion as Sorcerer sub-class (@Remathilis can comment on just how intolerable that'd be), but, by the same token, it'd be easier than creating a new class.
The idea was to replace extra attacks with granting attacks, and the concept that it could support is the much narrower vision of the Warlord taken up by the 13th Age 'Commander' class.
In brief, the Commander Fighter Archetype would gain an ability called 'Command' that takes the place of an Attack and grants an ally an attack (as he levels up, he'd choose from a list of other Commands that grant other sub-actions or whole actions). As a rather brutal limiting factor, following the Command would take the ally's Reaction. Most commands would be at-will, some might have a recharge mechanic of some sort (probably not a rest-recharge) or face some other situational limits to use, or might require the ally to rest before being able to follow that same command, again. It'd have to be limited to small set of Commands, as the Battlemaster is to maneuvers, because of the very limited design pace left to a fighter archetype, but, the relative power of said commands could at least start at the power-level of the attack being sacrificed, rather than being limited to the power of a 'rider.'
The result would still have the fighter's single-target DPR potenital while having options that could act as a force multiplier to other characters, so it'd be prettymuch impossible to balance - but that's a minor consideration in the context of 5e, let alone in the context of a wholly-optional (not in the Standard Game, 'opt-in') late addition to 5e. If a DM does introduce such a class, he'd also be expected to keep it relevant/contributing and balanced, as need in the course of the campaign.
[sblock="Commander Archetype"]This is rough and dashed-off, but might give a general idea:
Commander (Fighter Archetype)
There are leaders and there are followers, the archetypal Commander leads. Commanders may or may not have a formal rank in an actual military hierarchy, but even those that do not often affect such titles. Typically, the higher the Commander's level, the higher the rank he holds or styles himself as.
Those who model themselves on this archetype are decisive, charismatic fighters who exhort their allies to act without fear or hesitation in the heat of battle.
Voice of Command: The newly-minted Commander begins with two Commands, "Attack!" and "Rally!" These simple Commands are easily understood by any ally, even those that might have trouble understanding his language or hearing his exact words.
Drill: As he gains levels, the Commander can issue more and more sophisticated commands, but he must Drill his allies to respond them efficiently. At 7th, 10th, 15th, and 18th levels the Commander gains several commands, but can have his allies Drilled in only one of them. (Thus an 18th level commander can have his allies Drilled in 4 different commands, in addition to Attack & Rally). As part of a short rest, the Commander can swap out one Drilled command for the allies present throughout that rest. He can swap out all his commands in the course of an extended rest. (It may not seem like much of a rest, but it's just the convenient rest mechanic available).
Inspiring Leader: At 6th level, the Commander gains the Inspiring Leader feat instead of the fighter's 6th level Ability Score Increase. If the character already has Inspiring Leader, he can choose a different feat or ASI as normal.
3rd level Commands:
Attack!:
When the Commander notices or creates an opening, he uses a curt command, gesture or other signal to indicate the target to one of his allies.
The commander names the ally whom he commands and the enemy to target. The Ally can then make an attack using the weapon (or cantrip or other at-will ability that uses an attack roll) that he has ready against that target. Making the attack uses the Ally's Reaction instead of any action it might otherwise have required. If the Commander has Advantage against and/or is adjacent to the target, the ally's attack is made with Advantage. If the attack hits, it does additional damage equal to the Commander's INT mod. The Attack! command can be used in place of any attack the Commander is entitled to, at any time. There is no limit to how often an ally can be commanded to Attack!, but the ally must have a Reaction available to follow the command.
Rally!:
The Commander exhorts an ally to get back in the fight. Even an ally dropped unconscious or seemingly all but dead might be roused, so fierce and determined is the call.
The Commander chooses an ally who can see him or is within the sound of his voice (unconscious allies typically can't see, but aren't rendered deaf). That ally can roll one of his HD to regain hps, adding the Commander's CHA mod to the roll.
The Rally! command can be used in place of an Attack on the Commander's turn. The ally must have HD remaining to benefit from the Rally! command. If the ally has already been Rallied since his last rest, he must make a CON save (DC 15) to benefit from the Command. If he has already been Rallied once in the current encounter, the DC is 20. Rally! does not cost the ally an action, just HD.
This is IT!
You bolster an ally who seems un-ready for the coming battle.
When initiative is rolled, choose one ally who can see or hear you. You expend your Second Wind, and the ally gains the hps you roll as Temp hps. No action is required from you or the ally. You cannot use this command on the same ally again until that ally has completed a long rest.
7th Level Commands:
Get Behind Me! Use this command as your bonus action when you attack an enemy who is adjacent to one of your allies. If you hit, you inflict weapon dice damage, only (no bonuses), but the adjacent ally you command can use his reaction to move (through your space if necessary) so that you are now between him and the enemy you attack, this movement provokes no AoO from the enemy you hit. If you miss, the ally can disengage from the enemy as a Reaction, but must wait until his turn to move (such movement will not provoke an AoO from that enemy).
Charge! Use this command in place of an attack, and then move adjacent to an enemy. One of your allies may use his Reaction to move up to his speed and make a melee attack against that enemy, if he can reach it. You can use any other attacks you are entitled to before or after using this command, but any that you use to attack afterwards must be directed at the enemy you and your ally 'Charged.'
Get UP! Use this Command once as part of your own move on your turn. One ally of your choice can stand up as a Reaction.
10th Level Commands:
Form Up!: You allies can each move up to their speed as a reaction, the first ally to do so must end his move adjacent to the commander (if a grid is used, adjacent along a face, not a corner), creating a 'formation,' each other ally must end adjacent to an ally in the formation.
Push!: Use this Command as an Action onyour Turn. Your allies must be in formation with you. You and each ally who uses his Reaction to do so can make an attack against an adjacent enemy. Each must attack a different enemy. If any of the attacks hit, in addition to damage, each enemy adjacent to the formation (whether hit or attacked or not) is forced back 10' and the formation advances to stay adjacent to them. If an enemy would be forced into a dangerous area (like off a cliff, or into a fire) by the forced movement, he can make a STR save (DC = 8 + your proficiency bonus + the lower of your CHA mod or the highest STR mod in the formation) to stand his ground adjacent to the danger.
Get DOWN! When one or more of your allies is forced to make a DEX save to avoid or reduce damage, you can give this command using your Reaction. The allies drop prone immediately. If the save was to avoid damage, your allies have advantage on the save. If the save was to reduce damage, your allies take the reduced damage on a failed save, and no damage on a successful save. You cannot use this Command again until you have taken a short rest. An ally who followed this command but failed the saving throw cannot benefit from it again until he has taken a long rest.
15th Level Commands:
Fire!:
Acting as one, you & your allies unleash a devestating volley against your enemies
You designate a 'beaten zone' that you & your allies will attack into. The zone can be up to 20' deep and either 5' or 10' wide per attacker. Each ally who joins you in the attack must be able to make a ranged attack, and must use his Reaction. You and each ally who uses a reaction count as 'attackers.' If the zone is 5' per attacker or smaller, each attacker makes a full action worth of attack rolls (or a full-power attack), with a bonus to hit equal to your CHA modifier. If the zone is 10' per attacker, each attacker makes only one attack roll (or does only 1d of damage if he normally gets only 1 attack per acction, but does more than 1d of dmage with an at-will attack like a cantrip) and there is no attack bonus. Attacks are made against the average AC of all creatures in the zone (as determined or approximated by the DM). Once the number of hits are determined, the DM randomly assigns them among the creatures in the zone, with each one being struck no more than once in the case of a 10'/attacker zone, or twice for a 5'/attacker zone. This command uses your Action and you and your allies must be in formation. You and your allies must complete a short rest before you can use this command again.
It's a Trap! When an enemy or enemies is about to take a surprise round against one or more of your allies, you can issue this command to warn them. Instead of a surprise round, initiative is rolled normally. You cannot use this command again until you have taken a long rest. You also cannot use this command if any of the enemies acting in the surprise round were present the last time you used it.
18th Level Commands:
Stand Ready!:
You snap an ally out of the fog of battle.
Choose an ally who can see or hear you who has used or the ability to use his Reaction. He now has a Reaction available until the start of his next turn. You cannot use this Command on the same ally again until after the end of his next turn.
Don't Die On Me!:
The tenacity of life is an amazing thing, especially with you are there to help.
You touch (typically hold in your arms) an ally who is dying, taking ongoing damage that , or making a series of saves that could result in death or some similarly final fate. The ally makes an extra saving saving throw with your CHA mod as a bonus. If he succeeds, he is stabilized or the effect threatening him ends immediately. Failing this extra save has no effect (it does not count as a failed death save, for instance). Normally, using this command is an action, but, when an ally takes damage or fails a saving throw (including a death save) that would (or might) kill them, you can use this command as a Reaction if the ally is within one move of you, in which case you move to his side, suffering any consequences of that movement (if you are prevented from reaching him, you cannot complete the command).
[/sblock]