My question is, what is the reasoning behind using twister, is there a large advantage over using something like piercing orb? Is it an AP sink? If so, what is the advantage over using the Arcane Orb that pierces.
Now that I've spent an absurdly long time playing wizard, I can answer this with some confidence.
Energy Twister, specifically the Wicked Wind rune, has several major advantages over Arcane Orb (whatever rune).
This is most commonly used in CM Wizard builds as they rely on many proc effects.
Arcane Orb will only hit a target once, so your chances of proccing an effect is much smaller.