An MMO without the need for Healers?

I've been toying with the design for an open-world sandbox/PvE game for a while now, and one of the big traits of the game world so far is low-magic, meaning magic is more like that in Lord of the Rings than Arcanists. ...which poses a design problem: by default, PvE MMOs copy what WoW does, but without widespread access to magic, how can we have dedicated healers? How can the Holy Trinity survive?

Initially, I thought that perhaps non-magical healing would allow dedicated healers to exist, perhaps flitting about large battlefields, using potions, herbal salves and more mundane means to patch up injured soldiers that have retreated from the front lines. Indeed, if I have my way, that will be a viable build, and a useful function in a prolonged battle or siege, but what of shorter battles? Will healing even be a consideration, or should the fight simply be a damage race? What about small-group combat, that may not have enough members to spare a dedicated medic, lest the battle line crumble immediately? It is these considerations that lead me to a potential resource system that is akin to "Health" of other MMOs, but which answers my questions while remaining simulationistic.

Health
As in other MMOs, depletes with damage, refills outside of combat via healing effects (or natural regeneration, but over very long periods.)

Armor
An extension of the health bar, refills only when repaired or swapped, swapping armor takes a long time, and should be unlikely to be used as a tactic in any but the longest of battles, and surely not in active combat. Also, most armor only absorbs X damage per hit, an

Wards
Although likely to be rare, wards function like armor, extending the health bar, but are considered much earlier. Damage is assigned to the ward effect with the least remaining health first.

Dodge
Actively (based on player skill) prevents the first X attacks that would otherwise be hits on a player, refills in active combat up to Y%, as long as the player hasn't recently had an attack consider them. Has no chance to dodge an attack that you cannot detect. Refills fairly quickly to max when not in active combat.

Block & Parry
Actively (based on player skill) allows a player to prevent attacks with a shield or weapon. Prevents X damage before depleting. Both refill in active combat, even while being considered by attacks, however, both refill faster if a player hasn't been considered by any attacks recently. Parry should be more difficult to execute than Block, soak less damage before depleting than Block, and should fail on particularly massive attacks. Parry with two weapons should be slightly less potent than Block with a shield. It is my opinion that shields should not be breakable, except by special mechanics (or perhaps, not at all.)


When an attack "considers" a player, (that is to say, an attack's hit-box intersects a player's hit box,) the damage is assigned to a resource on the following priority table which is highest on the table and can apply to the attack in question:

1. Block
2. Parry
3. Dodge
4. Ward
5. Armor
6. Health

Healing magic is flavored as an infusion of "life energy" or "vitality," rather than "refilling your health stat." When a player is considered by healing magic, the healing applies to a resource on the following priority table which is highest on the table:

1. Health
2. Block
3. Parry
4. Dodge

Health is 1:1, 1 point of healing magic refills 1 point of health.
Block is 1:2, 1 point of healing magic refills 2 points of block.
Parry is 1:1.7, 1 point of healing magic refills 1.7 points of parry.
Dodge does not keep track of the amount of damage nullified, requires a constant X healing to refill a spent Dodge point. The time to refill a Dodge point naturally by time is constant.

What this all implies, is that by fluidly shifting a foe's focus, or cycling fatigued fighters to the rear of the battle lines, players can "catch their breath" and claim some fairly effective free healing in a situation without any "real" healers. Similarly, in a high-end squad incorporating dedicated magical healers, those not casting spells can use the same tactic to spread damage around, making healing itself less hectic, as well as maximizing the effects of natural recuperation, by ensuring that as many players are recovering at a given time as possible.