The late great Gary Gygax said
"It is quite unreasonable to assume that as a character gains levels of ability
in his or her class that a corresponding gain in actual ability to sustain
physical damage takes place. It is preposterous to state such an
assumption, for if we are to assume that a man is killed by a sword thrust
which does 4 hit points of damage, we must similarly assume that a hero
could, on the average, withstand five such thrusts before being slain! Why
then the increase in hit points? Because these reflect both the actual
physical ability of the character to withstand damage - as indicated by
constitution bonuses- and a commensurate increase in such areas as skill
in combat and similar life-or-death situations, the "sixth sense" whith
warns the individual of some otherwise unforeseen events, sheer luck,
and the fantastic provisions of magical protections and/or divine
protection. Therefore, constitution affects both actual ability to withstand
physical punishment hit points (physique) and the immeasurable areas
which involve the sixth sense and luck (fitness)."
I feel that regeneration is an excellent way to handle not necessarily health in an RPG, but survivability. Feels kind of weird in an FPS though. I just always picture my guy pushing 50 cal rounds out him like a bunch of slivers.
but BUT BUT!
There should be some way to become injured in combat that is not made better by taking a breather. When my character actually does get hit, it should have consequences. I'd really like to see lingering injuries that can only be remedied by potions or spells.
However, I'm afraid this won't happen and getting gored by a boar is nothing 5 minutes of breathing exercises can't fix.