Behaviour: when an NPC aggros on its master, it will automatically engage the aggressor. It will only attack currently aggro’d mobs, and will refrain from engaging other NPC’s unless aggro’d by the player (either by attacking it or entering aggro range). In PvP it will engage unaffilated players if:
-lock on is initiated by either party.
-its master attacks* a player (or its follower).
-a player attacks* its master (or the follower itself).
*Attacks blocked still cause the follower to react.
Pets will not use taunts/roars when in attack range, only if they are uable to reach target. Human thralls will use specific combo strings depending on enemies faced (e.g.: will use light, heavy, heavy, light 2H Sword combo when fighting groups; full heavy combo when fighting bosses)
Collision: either reduce the size of their collision or remove it completely to avoid situations where followers block doorways or push the player off cliffs. If the collision is kept, make is so that the follower can be pushed by its master, but not the other way around. I often find myself picking them up and placing them in guard mode just to move them out of my way before getting them to follow me again, but this is not a reliable workaround since it cant be done in areas that are claimed.
Inventory/equipment: either give thralls an inventory size on par with pets or give them two weapon loadouts (one for range and one for melee), so they can swap between them without occupying their already limited inventory slots. Thralls require a lot more work to convert than pets and I think it would make them worth all that trouble if they were able to carry loot as efficiently as the pets.
Feel free to add your suggestions to improve followers, or just share your best (or worse) experiences with the follower systems as it stands now