In combat, the thief had the potential to do some great one-shot damage to certain targets if the conditions were right. I wouldn't classify that as making the thief a consistent combat performer. The thief was never intended to be a strong combatant.This was all well and good because the system wasn't balanced around the round to round combat utility of each character.
What is this "great one-shot" damage you speak of? [Bold emphasis mine]
[sblock=D&D Rules Cyclopedia]Backstabbing: If a thief can sneak up on a victim, completely unnoticed, the thief may backstab—if he is using a one-handed melee weapon, he may strike at particularly vulnerable points of his target's body. (Though the ability is called "backstabbing," the weapon doesn't have to be a stabbing weapon. A thief can use this ability with a club, for example.)
When backstabbing, the thief gains a bonus of +4 on the attack roll; if the target is hit, the damage done is twice normal
(roll the damage for the weapon, multiply the result by two, and then add any pertinent modifiers).
If the intended victim sees, hears, or is warned of the thief's approach, the thief's attack is not a backstab; it is an ordinary attack, doing the damage appropriate for the weapon used.
When no battle is in progress, a backstab attempt may require a Move Silently ability check. The DM will make all the necessary decisions on that matter[/sblock]
[sblock=AD&D 1e PHB & DMG]Back stabbing is the striking of a blow from behind, be it with club, dagger, or sword. The damage done per hit
is twice normal for the weapon used per four experience levels of the thief, i.e. double damage at levels 1-4, triple at 5-8, quadruple at levels 9-12, and quintuple at levels 13-16. Note that striking by surprise from behind also increases the hit probability by 20% (+4 on the thief's "to hit" die roll).
Back Stabbing: Opponents aware of the thief will be able to negate the attack form.
Certain creatures (otyughs, slimes, molds, etc.) either negate surprise or have no definable "back", thus negating this ability. [/sblock]
[sblock=AD&D 2e PHB]Backstab: Thieves are weak in toe-to-toe hacking matches, but they are masters of the knife in the back. When attacking someone by surprise and from behind, a thief can improve his chance to successfully hit (+4 modifier for rear attack and negate the target's shield and Dexterity bonuses) and greatly increase the amount of damage his blow causes.
To use this ability, the thief must be behind his victim and the victim must be unaware that the thief intends to attack him. If an enemy sees the thief, hears him approach from a blind side, or is warned by another, he is not caught unaware, and the backstab is handled like a normal attack (although bonuses for a rear attack still apply).
Opponents in battle will often notice a thief trying to maneuver behind them--the first rule of fighting is to never turn your back on an enemy! However, someone who isn't expecting to be attacked (a friend or ally, perhaps) can be caught unaware even if he knows the thief is behind him.
The multiplier given in Table 30 [editors note=same as 1e PHB's multiplier table]
applies to the amount of damage before modifiers for Strength or weapon bonuses are added. The weapon's standard damage is multiplied by the value given in Table 30. Then Strength and magical weapon bonuses are added.
Backstabbing does have limitations. Fir
st, the damage multiplier applies only to the first attack made by the thief, even if multiple attacks are possible. Once a blow is struck, the initial surprise effect is lost. Second, the thief cannot use it on every creature. The victim must be generally humanoid. Part of the skill comes from knowing just where to strike. A
thief could backstab an ogre, but he wouldn't be able to do the same to a beholder. The victim must also have a definable back (which leaves out most slimes, jellies, oozes, and the like). Finally, the thief has to be able to reach a significant target area. To backstab a giant, the thief would have to be standing on a ledge or window balcony.
Backstabbing him in the ankle just isn't going to be as effective.[/sblock]
So lets get this all straight:
Thief, 9th level, +1 longsword, 16 Str (+2 in basic, -/+1 in AD&D)
Basic: +4 to hit, 2d8+3 damage. (5-19, av dmg 12)
AD&D: +4 to hit, 4d8+2 damage. (6-34 av dmg 20)
Average damage from a fireball, 9th level caster: 9d6 (9-54, av dmg 31, save 1/2), affects multiple foes
Average damage from a flame strike, 9th level caster: 6d8 (6-48, av dmg 27, save 1/2) affects multiple foes
Average damage from a fighter: 18/01 str, specialized with +1 longsword: +3 to hit, 1d8+6, 2 attacks (if both hit: 2d8+12, 14-28, av dmg 21), usable every round.
