That sounds about right. The gore damage might be a bit higher as well, or have augmented critical.
Yes, 3-24 does seem to be a lot of damage. I'd rather raise the damage than give them augmented critical - it says their horns are big, but there's nothing about them being sharp.
A regular boar's tusks are 1d8, going to Large would make them 2d6.
Make the armor boar's tusks 2d8?
Statwise I'm thinking we should increase the Constitution. A Large Advanced Boar has Con 21 and a Dire Boar Con 17, so how about Con 19?
What armour class do you fancy for them, the original's AC 3 translates to AC 17 in 3E, but I could see it going a bit higher, probably +12 NA or so, halfway between a Dire Boar's +6 NA and a Razor Boar's +17 NA.
I'll put in +8 NA for the time being to match the original's AC.
Maybe throw in DR X/- or light fortification as well?
Are we keeping it a poor Will save regular animal or making it a Dire animal?
Anyhow, here's a rough draft:
Armor Boar
Large Animal
Hit Dice: 7d8+28 (59 hp)
Initiative: +0
Speed: 40 ft. (8 squares)
Armor Class: 17 (–1 size, +8 natural), touch 9, flat-footed 17 [
+12 natural?]
Base Attack/Grapple: +5/+17
Attack: Gore +12 melee (2d8+12)
Full Attack: Gore +12 melee (2d8+12)
Space/Reach: 10 ft./5 ft.
Special Attacks: Ferocity,
"spiny defense?"
Special Qualities: DR 5/–, fortification, low-light vision, scent
Saves: Fort +9, Ref +5, Will +8
Abilities: Str 27, Dex 10, Con 19, Int 2, Wis 13, Cha 8
Skills: Listen +8, Spot +8
Feats: Alertness, Endurance, Iron Will
Environment: Temperate forests
Organization: Solitary or herd (2–12)
Challenge Rating:
5?
Treasure: None
Alignment: Always neutral
Advancement: 8–16 HD (Large); 17–21 HD (Huge)
Level Adjustment: —
Description
Armor boars grow up to 12 feet long and 6 feet tall at the shoulder, they weigh as much as X pounds.
Combat
Armor boars are dire animals, with all good saving throws.
Tactics.
Ferocity (Ex): An armor boar is such a tenacious combatant that it continues to fight without penalty even while disabled or dying.
Fortification (Ex): Whenever a critical hit or sneak attack is scored on an armor boar, there is a 50% chance (75% for Huge-sized armor boars) that the special attack is negated and its damage is rolled normally.
Spiny Defense (Ex): ?