Narcoma

Just for clarification: in the burn phase, how is it ever possible to get to the "Cast Arcane Orb if you do not have 4 Arcane Charges." part? The burn phase requires you to have Arcane power and Touch of the Magi ready, so TotM will always be ready at the start of the burn phase. Then, when I cast it, it'll provide 4 Arcane Charges. Does the AO part only get relevant when you would have to use Arcane Barrage before, but TotM still on CD?