Minions targeting unkillable things in Savannah boss fight

Minions shouldn't be able to target unkillable things. But indeed my ranged minions had a lot of fun shooting at northernly unkillable things not visible to the naked eye whilst I died horribly to an ignored Caedron, the Hyena Lord.

Side note, minions also batter Doryani in campaign after you've defeated him and he chatters away.