being a necromancer, increase your intellect because your skeletons will change. first you get normal ones,then ice,then fire and i am not sure if there are more
the baron is strong but if you are a bio user, have disrupt fully upgraded,then equip it as much as you can. He loses hp for his focus. Also have Integrity fully upgraded. So you don't need to use the leading strike move. Hope this helps kill him!