I was reading a post on the Alex Schroeder blog about how he has No clerics in his game. He gave reasons for this, half of which involve the use of healing magic and how it makes combat longer, devalues hit points as resource, reduces the need for recovery periods and puts pressure on the player playing the cleric to heal people all the time.
This does strike a chord with me that also resonates with the philosphy in Magic the Gathering that a card that grants just life gain does nothing but buy time and does not affect the board or card advantage. In gaming terms, if you are up against an impossible opponent, then healing is just going to give you a few more rounds to lose. It is also very true of some Fighting Fantasy books where having a stamina of 24, 40 stamina points worth of provisions and a potion that restores all lost stamina will not stop you getting killed if your skill is relatively low. However, if your skill is middling-high, then all that healing will make you invincible, so we have the worst of situations where either no amount of healing will not prevent you getting killed or the healing removes all sense of tension from the game.
I guess the only time healing is actually game changing is if it saves
you from a borderline loss, possibly due to bad luck. So mechanically,
the best healing would be healing that happens when your
hitpoints/stamina/endurance/whatever is below a certain value and then
it raises it to the "safe zone" to mitigate the effects of bad dice rolls made from good decisions.
I will endeveour to do this in my gamebooks. In my Legend of the Wayfarer world, there is magick (with a k, because that's cool) which is restricted to changing the tides of fortune in a small way. Anyhting else will require rare artefacts a tome of spells and performing complex rituals. There is also mysticism which allows the character to be in touch with the natural energies of the world and so they are more in tune with the spirits and fae, so they are able to communicate with them better, resist their influence and possibly ward them for a short time. However, there is no healing magic, apart from some gods of healing (and even for them, in dnd terms they are restricted to spells of 3rd level and lower). There are also healers, but they can only restore 1 Vitality Point per day, which means that f your character is on a quest that involves a time limit (and my updated rules include time tracking partly for this purpose), then that leads to interesting decisions. Of course, it is possible to buy some portable healing that you could use as much as you like, but it costs 5 times the price of a healer per Vitality Point, so it won't be used frivolously. This leads to some interesting situations where time, money and Vitality are a limited resource that has to be used wisely, which would mean more decision making. Of course, if there were clerics wandering the land offering healing or items that restore all lost Vitality on sale for a low price then this would remove the situations.
I know removing convenient healing might sound contentious as healing items are a nice safety net against things going wrong, but it might remove a lot of tension from a game where it makes too much of a difference or give you false hope and waste your time if it cannot make any difference.