When you're looking at Weapons in the auction house, Rare weapons with an element type will display that element as an image next to the item icon. (Lightning = lightning bolt streak / Arcane = Purple web / Poison = Green Spray of poison) Legendary weapons that have a specific element type will not have an element displayed next to the icon (i.e. Sun Keeper / Chantodo's) They appear as black weapons do on the AH, without any elemental representation when viewing the item's details.
This also appears to be the case with other set/leg items in other slots as well. Tal Rasha's Allegiance and Zunimassa's Trail also do not display the +element damage that they add.

Possible Auction house bug #2:
When using a 1 handed sword weapon, the auction house will compare it to and recommend 2 handed sword weapons. (Could we possibly get the option to filter recommended items by item slot/type (Glove/belt/pants) and quality (Rare/Legendary)?