The pet AI in general is abysmal. It feels as if the fairy was meant to be summoned and left alone. The most frustrating thing about Selene is I will tell her to use the melee skill speed buff and she then overwrites it with the spell speed buff as soon as it is off of CD. Why don't the buffs stack anyway? There is no real fear of it being overbalanced. The only work around is to tell her to cast the spell speed buff and then overwrite it yourself for melee heavy parties. These points are just the tip of the iceberg when it comes to pet micro though.