Actually:A guy held immobilized for a whole minute, and you couldn't just slit his throat? Nope, not according to the rules.
Note the part in bold. Note also that if this procedure were inadequate to the imagined situation, then another could be substituted.DMG said:Magically Sleeping or Held Opponents: If a general melee is in progress, and the attacker is subject to enemy actions, then these opponents are automatically struck by any attack to which they would normally be subject, and the maximum damage possible according to the weapon type is inflicted each time such an opponent is so attacked. The number of attacks or attack routines possible against such an opponent is twice the number normally allowed in a round. Otherwise, such opponents may be automatically slain, or bound as appropriate to materials at hand and size, at a rate of one per round.
Time factors in AD&D can indeed be irksome if one gives them much thought, but the same holds for those in 3E and 4E.