Dire Charm costs 9 AA points at level 59 minimum before you can get it ( And you need to have spent AA in level 51 and 55 type AA)
Is it useful? As a chanter I found it pretty good, but think it through. As a Chanter I have big hastes and slows which can even up most fights LOL. And I would have some nice processing summoned mage weapons, belt for HP and a mask for haste. ( even if they dont work I give the pets the items, you never know!)
And then I use my illusions to make the pet into a Werewolf or Scarecrow with small life tap.
In Plane of Valour the small frog was extremely powerful as a damadge add to a main tank, to the point we could easily heal using a Druid and often never dropping below 90% for main tank.