This question has been coming up a lot lately, so I may have to write it into the guide. Draught is always worth using during Execute. You'd need ~30-40 stacks of Juggernaut for Execute damage to match Draught, which isn't common. Draught is also rage neutral, so using it buys more Executes.
The ideal way to use Draught during Execute is:
BC - Execute - Execute - BT - Draught - Execute
- Preferably go into BC already Enraged, but there's no need to delay Battle Cry excessively to do so. This will cause Draught to fall out of Frothing, and possibly even part of Battle Cry, but it's far more rage efficient than overcapping for 3-5s.
- Obviously if the fight is expected to end immediately after your Battle Cry, then ignore the rage benefits and simply use Draught first