Oh, you absolutely can be. You don't track negative hps and accumulate down to your negative max. It's just, low-level critters can be instantly killed if you hit them for that much all at once. Once you're down, additional hits inflict automatic death save failures. Y'only get 3 of those.
They consume healing resources - HD, and, more importantly spell slots.
It doesn't appear you understood anything I said.
Death save failures aren't instant death for any level of PC unless deserved (such as a low-level party taking on a dragon or giant) or extremely unlucky (an orc doing max damage against a 1st level Wizard with CON penalties) - those three death save failures are mixed in amongst your chances to make the death saves, or have a party member cast a cure spell or use the medicine skill. Unless somehow the initiative order and dice fate is such that the unconscious PC is the last in initiative order and the remainder of the NPCs all go next
and all decide to target the PC who is no longer a threat (as opposed to the rest of the nasty PCs ready to kill the NPCs with their stabby weapons)
As to "consuming" healing resources? Anything that automagically resets itself after a certain point in time or can be used an infinite number of times isn't a healing resource. Your use of HD to miracle yourself healthy recovers itself after 8 hours with no deliberate decision to do so, unlike burning a cure spell or downing a potion. Likewise use of the Medicine skill is essentially free.
And - you don't even need to expend any of that to be 100% combat effective - all you need is one hour.
A PC can go from on death's door to 100% combat effective within one hour because you automagically regain 1 hp in as little as one hour after stabilizing since you don't track hit points below 0:
1st-level PC with 10 hp takes 19 points of damage. PC drops to 0 hp and goes unconscious. Three death saves or one successful use of the Medicine skill by a party member renders PC stabilized (and, by-the-by, since both the death save x 3 rolls or the Medicine skill check x 1 roll are at DC 10, it makes no sense whatsoever to
not have a low-level follower whose only job is to render first aid). No healing spells used. PC lays there for d4 hours (as little as 1 hour) and automatically gain 1 hp. PC is now conscious and 100% combat effective, having access to all of his spells, abilities, and equipment.
