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"