Point 1: The Cleric is using MAGIC to heal people almost instantly (upon casting a spell).
Point 2: That kind of "medical miracles service" is available in AD&D (as you cite) ... but not so much in Traveller.
Point 3:
If you remove the "miracles on demand Cleric" from the scenario that you're describing ... in order to "translate" the gameplay experience into Traveller terms ... then being reduced to ZERO or NEGATIVE HP pretty effectively removes people from being combat relevant, relegating them to the status of non-combatant and probably slain.
It's a LOT easier to recover from damage taken in AD&D ... the most common way being to just spend spell slots on miracle magics.
Damage in Traveller ... isn't so easily countered/negated, so it "hurts more" (in the
that will leave a mark sense) compared to AD&D.
So ... if you take your AD&D Cleric scenario and
remove the Cleric from it ...
{ significant look }