From Lu Li's memory, there were indeed three pieces of Legendary equipment.
No matter how difficult the mission, three pieces of Legendary equipment rewarded in one go would indicate a quest that had significant ramifications for Dawn's storyline.
There was a difference between his memories and reality. Something must have happened in between for there to be five items.
In fact, Lu Li wasn't wrong in his thinking.
Why were there five pieces? One aspect was due to his military rank. Initially, when Lu Li defeated the Blackrock Monster in Burning Steppes, Marshal Windsor saved hundreds of soldiers from the Alliance, which earned him his rank of Lieutenant. This was the lowest military rank. At first it felt like it wasn't much use, but this military rank represented Lu Li's success in being accepted by Stormwind City's military HQ and aristocracy.
