It is possible to craft several of these items without defeating Lord Incendius. It takes him several seconds to circle the anvil. If timed correctly, you should be able to finish crafting an item before dying.
A player who has Direbrew's Remote from the Brewfest seasonal event can quickly access the Black Anvil without having to go through the rest of the instance. The remote takes the player to the Grim Guzzler, and once the back door is opened (doable several ways), the player can turn to the right after going through the door and drop down onto the bridge where the anvil is located.