Given the current hp system it makes no sense to have a resource that restores hp. As better mathematicians than me have pointed out countless times, there is little difference between giving the healing ability and giving more hit points, except that the second wind (whatever you call it) is more complicated and introduces resource management. It's bad game design even before you start talking about the plausibility issues.
From a purely mathematical point of view, certainly, but this (a) ignores the dramatic value of a heroic recovery and (b) assumes that the recovery requires no (limited) resources to enact.
It gives them that sense only if they don't realize the mathematical reality (i.e. that this healing is basically just more hit points). For a new player, maybe it has that effect, but it doesn't hold up to any real scrutiny.
It is only "just more hit points" if it requires no limited resources to use. This is wrong on at least one count, ideally (from my point of view) from two.
The first count is that the recovery requires an action in the action economy. Given that you are in a conflict in which both sides act, that makes "actions" a precious resource; second wind takes an action, ergo it is not "just the same as more hit points".
The second count is that, if you have "hit dice" or "healing surges" or whatever nomenclature passes muster under the collective sense of aesthetics, then it costs these "long term hit points" to use second wind, making it extremely unlike "extra hit points" indeed.
Second Wind is basically "in-combat" healing. The more of it the party has available... the more it gets used, and the longer combats become.
If we are really looking for "shorter" and "less-grindy" combats... Second Wind runs directly counter to that. It's just more HP the monsters have to grind through. Same holds true for Potions of Healing and Cure Wounds spells used within combat. All of them extend combat.
As [MENTION=17106]Ahnehnois[/MENTION] has pointed out in his post that I replied to above, if all you are concerned about is number of hit points then starting hps and second wind recovery are indistinguishable. This means that, for long combats, the sum of hit points available is all that matters, so you could simply reduce both initial and recovered hit points until you get to the shortness of combat and degree of randomness you prefer. In other words, if the in-combat healing is part of the design, it is irrelevant to the combat duration, which simply relies on the total number of hit points available. Personally, I prefer more rather than less, up to a certain point, but if you want wham-bam-thank-you-ma'am fights then just halving all hit points (including healing results) should work a treat.
I'd say have the lower numbers as "core" or "basic" or whatever, and I'll just double them as a "module", but that would reduce the granularity available.
Damage mitigation and defensive effects, definitely. Temporary hps, probably OK in my book. Healing, not unless the character has a healing ability and is using the AP to duplicate or boost it in some way. Given the mathematical similarity, temp hp is less reality bending; why not just stick with that?
What on earth is "reality bending" about taking a breather and gaining extended endurance in a fight? Only if hit points are "meat" does that make sense - and hit points as "meat" don't make sense to begin with...
