Power Promotion has been a major source of the lag and performance issues because of the amount of data it generates. To create a smoother gaming experience, it was necessary for us to make some significant changes here, effective with the 6.6 update.

With the new process, auto-farming is removed. You'll still be charged Gold, Stamina, and Hero XP, but will just see a streamlined promotion to the new Rarity. The new system doesn't use any Badge Bits from your inventory, just the full Badges. Full Badges and Badge bits are no longer shown because Power Promote now burns only exactly what you need, resulting in no extra Badges or Bits.

You can still Power Promote when the Gold cost shown is higher than what you have on hand. This is because the earned Gold in the Power Promote process is calculated into the resources that will be used to complete the promotion.