My Beetles have RC+AP. When i'm using a Beetle, it's to deliver debuffs to the opponent so that everyone dishes out more damage. Rune Corruption halves the victim's Resists, and Armor Pierce applies a debuff to the victim where they take +10% Damage for 3 seconds (even affects WoD). Giant Beetle for Physical weak foes, Fire Beetle for Fire weak foes, and Frost Mite (these can get some monstrous stats) for Cold weak foes.
I find Poisoning to be a waste on them, it takes away from their use of RC/AP, Magery opponents will frequently cure it, and even if it's not cured, it delivers such little damage to most foes, plus it makes it more difficult to switch the pet to another target.