It looks like the Necromancers' pet doesn't have a clear pathing at the moment.
For a Necromancer it's possible to send e. g. inside keeps from tower to tower without need of the pet to move downstairs and back upstairs on other tower. It just "warps" between towers so attack / passive / attack makes it even impossible to handle.
Also there is the issue that if the player ports inside the pet is not ported with the necromancer and the pet moves directly like a ghost into the walls if it was outside before.