Has there been a definitive answer that Tactician mode doesn't affect AI or mobs?
It alludes that it does when you pick the option in game.

Here's what the difficulty settings do:

DOS2

EASY:

new entry "CasualPlayer"
type "Character"
data "ArmorBoost" "30"
data "MagicArmorBoost" "30"
data "Vitality" "50"
data "DamageBoost" "50"
data "Accuracy" "5"
data "Dodge" "5"

new entry "CasualNPC"
type "Character"
data "ArmorBoost" "-50"
data "MagicArmorBoost" "-50"
data "Vitality" "-40"
data "DamageBoost" "-50"
data "Accuracy" "-15"



NORMAL:

new entry "NormalPlayer"
type "Character"

new entry "NormalNPC"
type "Character"



HARD:

new entry "HardcorePlayer"
type "Character"

new entry "HardcoreNPC"
type "Character"
data "ArmorBoost" "50"
data "MagicArmorBoost" "50"
data "Vitality" "50"
data "DamageBoost" "50"
data "Accuracy" "10"



DOS EE Settings:

EASY:

new entry "CasualPlayer"
type "Character"
data "Vitality" "80"
data "ChanceToHitBoost" "30"


new entry "CasualNPC"
type "Character"
data "Vitality" "-50"
data "ChanceToHitBoost" "-25"


NORMAL:

new entry "NormalPlayer"
type "Character"
data "Vitality" "15"

new entry "NormalNPC"
type "Character"


HARD:

new entry "HardcorePlayer"
type "Character"


new entry "HardcoreNPC"
type "Character"
data "Vitality" "20"
data "ChanceToHitBoost" "20"