I've always found it a little weird that you just don't see mc's who's main occupation isn't stab monster/enemy with sharp metal stick.
Because from a meta perspective, Healers suck and Tanks are Boring. Take D&D, 3rd.
Mathematically, healing in combat is bad. It’s part of the whole conservation of action thing. You can only do so many things in a round. If you spend your action healing, you need to heal more damage then the enemy inflicts to make it worth your time and effort. In hand to hand combat, where your enemy is using full round actions to attack, damage will outpace healing.
This is not a video game. Healing in combat is a last resort, or something you do when you can’t do anything else. Heal and mass heal are good, because they often outpace the damage you take in a round, plus mass heal can do damage against undead. Stick to using cure light wounds or lesser vigor in a wand to heal outside of combat. Gold to hit point healed cost ratio proves that a lesser vigor wand is the best for healing, if you have a few minutes to heal.
That said, sometimes you have a few rounds. Make sure to keep one or two healing potions that are as powerful as you can afford in your equipment list. Maybe the enemy will retreat for a few rounds to come at you from another direction. That’s when using your actions to heal is important, and you might not have 40 rounds to do it in.
At-will healing, like regeneration, sounds nice, but in play isn’t that useful, unless you are in a gauntlet. What that means is, instead of the typical 3 combats a day, you are not going to have a chance to rest and heal. There will be no spell recovery, and the only thing you can do is push on or fail. Then unlimited healing is nice. Otherwise, one ring of regeneration can buy a dozen wands of lesser vigor and the wand will occupy much less of your WBL.
There is one exception. If your allies have been debilitated, and healing them returns them to combat ready status, do it. This covers poison, paralyzing, being 0 to -9 hit points, weird diseases, and anything else that renders your allies from being effective. Bringing an ally back to fighting trim is worth taking the time to heal, because it acts as a force multiplier and increases the over all effectiveness of your side.
I bring this up, because Most RPGs follow the D&D format. Death is typically Binary as far as HP are concerned.
Which is more dangerous to you when you lose initiative? A level 10 fighter with one hit point, or a level 10 fighter with 100 hit points? Trick question, they are equally dangerous.
It takes a while to sink in, but D&D (and most RPGs) have a binary nature to it when it comes to hit points. You are just as dangerous with one hit point as with a hundred. Once you reach zero, you drop, but until then you suffer no ill effects. So a fireball that wounds a group of goblins is only useful in setting up a group of targets for a fighter with mighty cleave to go to town. It is far better to focus damage on one target, move to the next, then the next.
Another example, if you have a magic missile that will do 5 points of damage and you have a wounded target that is almost dead with one hit point left, and a target that has ten hit points, which one would you attack?
Well, in the real world, it would seem like the almost dead target would waste 4 points of damage, but in D&D, dropping a target this round means one less enemy to attack you next round. Better to over kill the wounded, then to leave two targets up to fight you next round.
As for tanks, well, depends on the setting. You see, Video games have set rules and thinking outside the box isn't really an option. IT IS DEFINED BY THE BOX, but a story/manga is more like a table top RP session, and therefore, tanks suck.
In most video games, Wading through a hail of arrows, laughing as you shake shrapnel out of your beard. Sounds fun. But in D&D, when you get to a level where you can do that, the enemy is using far more save-or-suck attacks. Furthermore, if the enemy is ineffective against you, your allies aren’t tanks. So they will just switch targets and pick them off one at a time, saving you for last. Most Stories/Manga get around this by allowing Taunt/Draw Aggro Spells, but honestly, yer a one trick pony.
Being a damage sponge isn’t good in a game where whittling your enemies down has no effect until the last hit point. Again, the binary nature of hit points makes this sort of build less than optimal. That said, they can be fun, just understand what you are getting into.
From a WRITING perspective, it's dull as shit. When you play a lot of videogames, it's simple: You win when everything else is dead.
When you table top, or by extension, write a story, Damage isn't everything. A barbarian who deals 1 million damage with a great-axe is useless against enemies who can fly. A charm person spell can defeat an enemy instantly, and is useful outside combat too. Hindering or weakening your enemies makes them easier to kill. Spellcasters have far more options than direct damage, while non-casters have a harder time attaining them.
You see, non-casters are usually stuck with different ways to inflict damage and that’s about it. Whereas a caster often have a number of save-or-suck attacks at their disposal. The over all goal is basically to render your enemies unable to fight, not to kill them. Hold person works just as well as 400 hit points of damage.
Winning is not about dead bodies at your feet. It’s about crippling your enemies so you can kill them, or capture them, or whatever you wish to do. By the binary nature of D&D’s hit point system, a paralyzed NPC is the same as a dead NPC is the same as a nauseated/entangled NPC. If the NPC can’t do anything, it’s the same as winning.
So, for having a spellcaster who can DO all these alternate ways to defeating an enemy, it's interesting. How many stories can I write about
Bob The Barbarian stood there, acted annoying to draw aggro, and sucked up damage... again.
And
Jill The Healer cast Mass Cure Moderate Wounds... again.
Or...
Mystic Ranger/Erudite/Archivist/Eldolonancer who is Major Bloodline titan, moderate bloodline gold dragon, minor bloodline doppleganger. because I can be casting 4th level spells and 3rd level psionics as a 4th level character, when I should, at best, only be casting 1st level ANYTHING. Yeah, OP as hell and an abuse of the rules concerning character creation to a degree where most DMs would look at this monstrosity and say, "Uhh... You realize you had to die and be RESURRECTED at least ONCE for this insane combo to work, right?"
So who do you wanna read about more?
The Character created by a power gaming munchkin, or the adventures of Bob and Jill, The Damage Sponges?