Allyn Gibson wrote:
The chronology doesn't line up for that. The assault on Dol Guldur would take place at roughly the same time as Smaug's death. It's because the White Council was successful in driving the Necromancer from Dol Guldur that Gandalf is able to go back to Erebor when things go all pear shaped there in the wake of Smaug's death.
Actually, in the book, Gandalf "was in fact finishing his other business [at Dol Guldur] and getting ready to come in search of Thorin's company" before Bilbo and the dwarves even reach Lake Town. Not that PJ is obligated to stay true to the timeline, but he'd have to move the battle at Dol Guldur, significantly, to line up with Smaug's demise.