AD&D: The Relative Efficacy of Monster Summoning I

This DF thread inspired me to conduct a quick simulation to determine the relative efficacy of MS I vice other level III spells (namely, direct damage): http://www.dragonsfoot.org/forums/viewtopic.php?f=1&t=36328&p=733450#p733450

WHAT DO YOU GET?

01-10: Demon, manes - HD1 AC7 1-2/1-2/1-4 (+1 magic weapons to hit, undead immunities)
11-25: Goblin (Dwarf) - HD1-1 AC6 1-6 (chance for missile weapons)
26-40: Hobgoblin (Elf) - HD 1+1 AC5 1-8 (chance for missile weapons)
41-55: Kobold (Halfling) - HD 1/2 AC4 1-4 (chance for missiles)
56-70: Orc (Gnome) - HD 1 AC6 1-8
71-00: Rat, Giant - HD 1/2 AC7 1-3

This discounts the monsters for evil summoners, but they are generally superior, I think.

Thus you have:
30% - HD 1/2 AC7 1-3
15% - HD 1/2 AC4 1-4
15% - HD1-1 AC6 1-6
10% - HD1 AC7 1-2/1-2/1-4
15% - HD 1 AC6 1-8
15% - HD 1+1 AC5 1-8

So, on average, you get 5 x 1-1 HD critters, AC 6ish for 1d6 damage. Sometimes its better (hobgoblins are pretty robust), sometimes it sucks. However, the GM may "personally select" the numbers appearing if the monster is parcticularly weak, so let's assume that it balances out.

We'll consider the usefulness against three monsters: A standard low, mid, and high level threat. Our low level threat will be an orc (with a pie). The mid level threat an ogre. And high level threat a hill giant. Usefulness will be measured by how much damage can be inflicted before they are splattered, on average.
LOW: HD1 AC6 1-8
MED: HD4+1 AC5 1-10
HIGH: HD8+2 AC4 2-16

SURVIVEABILITY:

Damage sustained each round:
LOW LEVEL THREAT: 40% * 4.5 = 1.8
MED LEVEL THREAT: 60% * 5.5 = 3.3
HIGH LEVEL THREAT: 75% * 9 = 6.75

Rounds that a critter with 3.5 HP can survive:
LOW LEVEL THREAT: 1.94 (2)
MED LEVEL THREAT: 1.06 (1)
HIGH LEVEL THREAT: 0.52 (min of 1)

DAMAGE INFLICTED:

Damage Inflicted on threat per round per monster:

LOW LEVEL THREAT: 35% * 3.5 = 1.225
MED LEVEL THREAT: 30% * 3.5 = 1.05
HIGH LEVEL THREAT: 25% * 3.5 = 0.875

Damage Inflicted on threat over expected lifetime of monster:
Assumes that there is a 1:1 ratio, i.e., one threat monster for each summoned monster.
LOW: 2.45
MED: 1.05
HIGH: 0.875

Total Damage Inflicted (multiply by 5 monsters, on average):
LOW: 12.25
MED: 5.25
HIGH: 4.375

Comparison to 1d6 per level save for half (as from a fireball):
LOW: 25% for 1.75 + 75% for 3.5 = 0.4375 + 2.625 = 3.0625 / level of caster
MED: 40% 1.75 + 60% 3.5 = 0.7 + 2.1 = 2.8 / level of caster
HIGH: 55% for 1.75 + 45% for 3.5 = 0.9625 + 1.575 = 2.5375 / level of caster

ANALYSIS:

If you send summoned trash in to fight mano-a-mano, its not very efficient compared to nuking with a fireball. However, if the summoned trash can gang up on a single threat, extend its life expectancy (through defensive buffs or use of missile weapons, for example), or increase offensive potency (bless, prayer, haste, etc) then it will become more effective, numerically speaking.

Summoned trash also has a few other advantages. It can hold a line whether needed as a rearguard or instant bodyguards -- fireballs do not protect squishy mages or buy time for a retreat. It is a beyond visual range weapon: you can summon stuff, send it into a room, and wait for the shooting to stop in order to soften up targets; very few spells do not have line-of-sight requirements so this is big. Conjured critters take attacks that would have otherwise been aimed at PCs, thus giving the spell defensive value as well. It is also useful for problem solving, tricks & traps, etc. Finally, summoned trash is discriminate; you can use it when a large mixed melee is going on and you don't want to risk friendly fire.