Which system/edition? In most, your healer isn't doing his job right. Or is "not always" the same as "rarely"?
It's a modified 1e system. And the healers do what they can, but sometimes one of two factors rears its head: a) the healers don't have enough spells to get everyone all the way up to full, and-or b) one or more people in the party have recently been too badly hurt to be able to take cures for a while, above a fairly low threshold.
To explain: we use a body point-fatigue point system, and if you've recently been below 0 h.p. you cannot usually be cured above full b.p. (most people have 3-5 b.p., and f.p. are what you get as you level up) until some time has passed; the length of time depends on how far down you went and what was used to cure you.
??? don't understand your need to make healed characters unstable again? The first preference depend on your definition and use of HP (the time until the character expires or really blood lost and wounds continuing to open.
I think we all agree that below 0 is real actual damage, injury, etc. that will eventually be fatal if not treated. Patching someone up from -8 to -4 does not fully count as "treated", and said victim will still eventually die if not further helped out; only it'll take longer due to temporary stabilizing caused by the patching up.
0 h.p. is the tipping point. Above 0, you'll eventually recover on your own given enough time. Below 0 you'll die on your own given enough time. Right at 0 h.p. is saving throw territory.
How is a fixed healing time based on con and HD heal the wizard faster? Because he took less damage???
I didn't say Con bonus and HD, I said Con bonus and level; and was referring to any other system as well where the amount recovered overnight is a flat number.
To clarify:
Wizard and Fighter are both 5th level. They have the same Con bonus; let's say +1. So, each will rest back 6 h.p. per night. If no other healing is available, this happens:
Wizard goes to sleep at 7 h.p. out of 15.
Fighter goes to sleep at 18 h.p. out of 40.
Wizard wakes up at 13 of 15, pretty close to full.
Fighter wakes up at 24 of 40, still a fair way from peak condition.
After a second night the wizard will be fine while the fighter will still only be at 75%. Any time they both lose the same fraction of their h.p. (both are at 1/2, both are at 1/4, etc.) the wizard will always recover faster; and this doesn't make sense.
BUT if you use a percentage of full h.p. as the heal rate instead, watch what happens:
Let's set the heal rate dial at 20%. So, in the above example the wizard will get back 3 h.p. per night and the fighter will get 8; so after 3 rests they'll both be just nicely to full. They rest up at the same rate relative to each other and relative to how many h.p. they were short as a fraction of their maximum and - assuming no other interference either good or ill - will recover to full h.p. in the same amount of time*. If most h.p. are defined as something other than debilitating injury it only makes sense they'd be recovered at about the same relative rate by all involved.
* - or very close, depending on math-y things like rounding error.
Lanefan