Just like with the Conserve Phase, the Burn phase does not follow a strict rotation but rather a priority list. This phase is heavily tied to the cooldown of your Evocation and can only be started when you are at 4 Arcane Charges.
1. Cast Arcane Power.
2. Cast Arcane Missiles.
3. Cast Arcane Blast if you have more than 50% mana.
4. Cast Evocation if you have less than 50% mana and 4 stacks of Arcane Charge.

At the start of the fight and whenever Evocation Icon Evocation is about to come off cooldown, you need to start the Burn Phase and burn your Mana. Before doing so, make sure that you have 3 charges of Arcane Missiles Icon Arcane Missiles and 4 stacks of Arcane Charge Icon Arcane Charge.
Your rotation during the Burn Phase is the same as the Conserve Phase, with three changes.
-Arcane Barrage should never be cast during the Burn Phase, because you want to remain at 4 stacks of Arcane Charge for the entire Burn Phase.
-Arcane Blast should be cast without Mana restrictions. Your goal is to burn your Mana, and the only way to do so is to keep casting Arcane Blast.
-When your Mana drops below 50%, use Evocation to get back to full Mana (interrupt the channel when you reach 100%). After that, resume your Conserve Phase.