I am currently playing on tactican and find It a bit too easy. I have already beaten the game on normal and that was too easy. I did not even have to use barrelmancy or pack a bag of explosives to insta kill someone.
If I might suggest give the npcs on higher difficulties potions, elixirs, coatings, and high level spells. I would love to fight npcs who would try to freeze me or summon hordes of monsters and try to outnumber me. Give Gortash a haste potion. Add an option that would defy the option to spam save/load like a checkpoint or a limited amount of saves per act.
These are all suggestions meant to make the game more complex, challenging and more fun for hardcore players instead of increasing the hit points of enemies.