Being legendary comes with many perks. Sure, there is the training point, the title, among others, but you also receive access to the dungeons Waterworks and Tower of the Helephant. These instances are supposed to be the toughest in the game, and have very tough enemies.
I just made legendary, and I am looking for other Wizards to do the WW or the TOTH dungeons. I won't be in game this Monday-Thursday, but I am sending out and SOS to any wizards who want to do the dungeons.